[gdb/testsuite] Don't pass -fPIC to gdb_compile_shlib
When running test-case gdb.base/info-shared.exp, I see in gdb.log:
...
Executing on host: \
gcc ... -fPIC -fpic -c -o info-shared-solib1.c.o info-shared-solib1.c
...
The -fPIC comes from the test-case:
...
if { [gdb_compile_shlib $srcfile_lib1 $binfile_lib1 \
[list additional_flags=-fPIC]] != "" } {
...
but the -fpic, which overrides the -fPIC comes from gdb_compile_shlib.
The proc gdb_compile_shlib adds the -fpic or similar dependent on platform
and compiler. However, in some cases it doesn't add anything, which is
probably why all those test-case pass -fPIC.
Fix this by removing -fPIC from all the calls to gdb_compile_shlib, and
ensuring that gdb_compile_shlib takes care of adding it, if required.