GCN: Don't emit weak undefined symbols [PR119369]

GCN: Don't emit weak undefined symbols [PR119369]

This resolves all instances of PR119369
"GCN: weak undefined symbols -> execution test FAIL, 'HSA_STATUS_ERROR_VARIABLE_UNDEFINED'";
for all affected test cases, the execution test status progresses FAIL -> PASS.

This however also causes a small number of (expected) regressions, very similar
to GCC/nvptx:

    [-PASS:-]{+FAIL:+} g++.dg/abi/pure-virtual1.C  -std=c++17 (test for excess errors)
    [-PASS:-]{+FAIL:+} g++.dg/abi/pure-virtual1.C  -std=c++26 (test for excess errors)
    [-PASS:-]{+FAIL:+} g++.dg/abi/pure-virtual1.C  -std=c++98 (test for excess errors)

    [-PASS:-]{+FAIL:+} g++.dg/cpp0x/pr84497.C  -std=c++11  scan-assembler .weak[ \t]*_?_ZTH11derived_obj
    [-PASS:-]{+FAIL:+} g++.dg/cpp0x/pr84497.C  -std=c++11  scan-assembler .weak[ \t]*_?_ZTH13container_obj
    [-PASS:-]{+FAIL:+} g++.dg/cpp0x/pr84497.C  -std=c++11  scan-assembler .weak[ \t]*_?_ZTH8base_obj
    PASS: g++.dg/cpp0x/pr84497.C  -std=c++11 (test for excess errors)
    [-PASS:-]{+FAIL:+} g++.dg/cpp0x/pr84497.C  -std=c++17  scan-assembler .weak[ \t]*_?_ZTH11derived_obj
    [-PASS:-]{+FAIL:+} g++.dg/cpp0x/pr84497.C  -std=c++17  scan-assembler .weak[ \t]*_?_ZTH13container_obj
    [-PASS:-]{+FAIL:+} g++.dg/cpp0x/pr84497.C  -std=c++17  scan-assembler .weak[ \t]*_?_ZTH8base_obj
    PASS: g++.dg/cpp0x/pr84497.C  -std=c++17 (test for excess errors)
    [-PASS:-]{+FAIL:+} g++.dg/cpp0x/pr84497.C  -std=c++26  scan-assembler .weak[ \t]*_?_ZTH11derived_obj
    [-PASS:-]{+FAIL:+} g++.dg/cpp0x/pr84497.C  -std=c++26  scan-assembler .weak[ \t]*_?_ZTH13container_obj
    [-PASS:-]{+FAIL:+} g++.dg/cpp0x/pr84497.C  -std=c++26  scan-assembler .weak[ \t]*_?_ZTH8base_obj
    PASS: g++.dg/cpp0x/pr84497.C  -std=c++26 (test for excess errors)

    [-PASS:-]{+FAIL:+} g++.dg/ext/weak2.C  -std=gnu++17  scan-assembler weak[^ \t]*[ \t]_?_Z3foov
    PASS: g++.dg/ext/weak2.C  -std=gnu++17 (test for excess errors)
    [-PASS:-]{+FAIL:+} g++.dg/ext/weak2.C  -std=gnu++26  scan-assembler weak[^ \t]*[ \t]_?_Z3foov
    PASS: g++.dg/ext/weak2.C  -std=gnu++26 (test for excess errors)
    [-PASS:-]{+FAIL:+} g++.dg/ext/weak2.C  -std=gnu++98  scan-assembler weak[^ \t]*[ \t]_?_Z3foov
    PASS: g++.dg/ext/weak2.C  -std=gnu++98 (test for excess errors)

    [-PASS:-]{+FAIL:+} gcc.dg/attr-weakref-1.c (test for excess errors)
    [-FAIL:-]{+UNRESOLVED:+} gcc.dg/attr-weakref-1.c [-execution test-]{+compilation failed to produce executable+}

    @@ -131211,25 +131211,25 @@ PASS: gcc.dg/weak/weak-1.c scan-assembler weak[^ \t]*[ \t]_?c
    PASS: gcc.dg/weak/weak-1.c scan-assembler weak[^ \t]*[ \t]_?d
    PASS: gcc.dg/weak/weak-1.c scan-assembler weak[^ \t]*[ \t]_?e
    PASS: gcc.dg/weak/weak-1.c scan-assembler weak[^ \t]*[ \t]_?g
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-1.c scan-assembler weak[^ \t]*[ \t]_?j
    PASS: gcc.dg/weak/weak-1.c scan-assembler-not weak[^ \t]*[ \t]_?i

    PASS: gcc.dg/weak/weak-12.c (test for excess errors)
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-12.c scan-assembler weak[^ \t]*[ \t]_?foo

    PASS: gcc.dg/weak/weak-15.c (test for excess errors)
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-15.c scan-assembler weak[^ \t]*[ \t]_?a
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-15.c scan-assembler weak[^ \t]*[ \t]_?c
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-15.c scan-assembler weak[^ \t]*[ \t]_?d
    PASS: gcc.dg/weak/weak-15.c scan-assembler-not weak[^ \t]*[ \t]_?b

    PASS: gcc.dg/weak/weak-16.c (test for excess errors)
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-16.c scan-assembler weak[^ \t]*[ \t]_?kallsyms_token_index
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-16.c scan-assembler weak[^ \t]*[ \t]_?kallsyms_token_table
    PASS: gcc.dg/weak/weak-2.c (test for excess errors)
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-2.c scan-assembler weak[^ \t]*[ \t]_?ffoo1a
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-2.c scan-assembler weak[^ \t]*[ \t]_?ffoo1b
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-2.c scan-assembler weak[^ \t]*[ \t]_?ffoo1c
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-2.c scan-assembler weak[^ \t]*[ \t]_?ffoo1e
    PASS: gcc.dg/weak/weak-2.c scan-assembler-not weak[^ \t]*[ \t]_?ffoo1d

    PASS: gcc.dg/weak/weak-3.c  (test for warnings, line 58)
    PASS: gcc.dg/weak/weak-3.c  (test for warnings, line 73)
    PASS: gcc.dg/weak/weak-3.c (test for excess errors)
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-3.c scan-assembler weak[^ \t]*[ \t]_?ffoo1a
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-3.c scan-assembler weak[^ \t]*[ \t]_?ffoo1b
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-3.c scan-assembler weak[^ \t]*[ \t]_?ffoo1c
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-3.c scan-assembler weak[^ \t]*[ \t]_?ffoo1e
    PASS: gcc.dg/weak/weak-3.c scan-assembler weak[^ \t]*[ \t]_?ffoo1f
    PASS: gcc.dg/weak/weak-3.c scan-assembler weak[^ \t]*[ \t]_?ffoo1g
    PASS: gcc.dg/weak/weak-3.c scan-assembler-not weak[^ \t]*[ \t]_?ffoo1d

    PASS: gcc.dg/weak/weak-4.c (test for excess errors)
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-4.c scan-assembler weak[^ \t]*[ \t]_?vfoo1a
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-4.c scan-assembler weak[^ \t]*[ \t]_?vfoo1b
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-4.c scan-assembler weak[^ \t]*[ \t]_?vfoo1c
    PASS: gcc.dg/weak/weak-4.c scan-assembler weak[^ \t]*[ \t]_?vfoo1d
    PASS: gcc.dg/weak/weak-4.c scan-assembler weak[^ \t]*[ \t]_?vfoo1e
    PASS: gcc.dg/weak/weak-4.c scan-assembler weak[^ \t]*[ \t]_?vfoo1f
    @@ -131267,16 +131267,16 @@ PASS: gcc.dg/weak/weak-4.c scan-assembler weak[^ \t]*[ \t]_?vfoo1i
    PASS: gcc.dg/weak/weak-4.c scan-assembler weak[^ \t]*[ \t]_?vfoo1j
    PASS: gcc.dg/weak/weak-4.c scan-assembler weak[^ \t]*[ \t]_?vfoo1k

    PASS: gcc.dg/weak/weak-5.c (test for excess errors)
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-5.c scan-assembler weak[^ \t]*[ \t]_?vfoo1a
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-5.c scan-assembler weak[^ \t]*[ \t]_?vfoo1b
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-5.c scan-assembler weak[^ \t]*[ \t]_?vfoo1c
    PASS: gcc.dg/weak/weak-5.c scan-assembler weak[^ \t]*[ \t]_?vfoo1d
    PASS: gcc.dg/weak/weak-5.c scan-assembler weak[^ \t]*[ \t]_?vfoo1e
    PASS: gcc.dg/weak/weak-5.c scan-assembler weak[^ \t]*[ \t]_?vfoo1f
    PASS: gcc.dg/weak/weak-5.c scan-assembler weak[^ \t]*[ \t]_?vfoo1g
    PASS: gcc.dg/weak/weak-5.c scan-assembler weak[^ \t]*[ \t]_?vfoo1h
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-5.c scan-assembler weak[^ \t]*[ \t]_?vfoo1i
    [-PASS:-]{+FAIL:+} gcc.dg/weak/weak-5.c scan-assembler weak[^ \t]*[ \t]_?vfoo1j
    PASS: gcc.dg/weak/weak-5.c scan-assembler weak[^ \t]*[ \t]_?vfoo1k
    PASS: gcc.dg/weak/weak-5.c scan-assembler weak[^ \t]*[ \t]_?vfoo1l

These get 'dg-xfail-if'ed or 'dg-skip-if'ed, (mostly) similar to GCC/nvptx.

	PR target/119369
	gcc/
	* config/gcn/gcn-protos.h (gcn_asm_weaken_decl): Declare.
	* config/gcn/gcn.cc (gcn_asm_weaken_decl): New.
	* config/gcn/gcn-hsa.h (ASM_WEAKEN_DECL): '#define' to this.
	gcc/testsuite/
	* g++.dg/abi/pure-virtual1.C: 'dg-xfail-if' GCN.
	* g++.dg/cpp0x/pr84497.C: 'dg-skip-if' GCN.
	* g++.dg/ext/weak2.C: Likewise.
	* gcc.dg/attr-weakref-1.c: Likewise.
	* gcc.dg/weak/weak-1.c: Likewise.
	* gcc.dg/weak/weak-12.c: Likewise.
	* gcc.dg/weak/weak-15.c: Likewise.
	* gcc.dg/weak/weak-16.c: Likewise.
	* gcc.dg/weak/weak-2.c: Likewise.
	* gcc.dg/weak/weak-3.c: Likewise.
	* gcc.dg/weak/weak-4.c: Likewise.
	* gcc.dg/weak/weak-5.c: Likewise.