gdb, testsuite: Handle unused compiler option fdiagnostics-color=never.

gdb, testsuite: Handle unused compiler option fdiagnostics-color=never.

The 'univeral_compile_options' in gdb.exp file only verifies the support
of '-fdiagnostics-color=never' for the "C" source file.  So while running
tests with assembly source file (.s), many of them are not able to run
on icx/clang compilers because '-fdiagnostics-color=never' option is not
supported.  This problem is not seen for the ".S" assembly source files so
these files are not handled separately.  After this change, this function
is split into multiple functions to check the support for different type
of sources individually.

Before this change, in the case of clang and ICX compiler, this error is
shown for assembly source files (.s):

'''
icx -fdiagnostics-color=never -Wno-unknown-warning-option -fno-pie -c -O0 -o
amd64-entry-value0.o gdb/testsuite/gdb.arch/amd64-entry-value.s (timeout = 300)

icx: warning: argument unused during compilation: '-fdiagnostics-color=never'
[-Wunused-command-line-argument]

gdb compile failed, icx: warning: argument unused during compilation:
'-fdiagnostics-color=never' [-Wunused-command-line-argument]

UNTESTED: gdb.arch/amd64-entry-value.exp: failed to prepare
'''

Similarly this error is shown for the clang compiler:

'''
clang  -fdiagnostics-color=never -Wno-unknown-warning-option -fno-pie -c -O0
-o amd64-entry-value0.o gdb/testsuite/gdb.arch/amd64-entry-value.s

clang: warning: argument unused during compilation:
 '-fdiagnostics-color=never' [-Wunused-command-line-argument]
'''

Approved-By: Tom Tromey <tom@tromey.com>