compiler-gcc: Suppress -Wmissing-prototypes warning for all supported GCC #3500

Job	Run time
set-matrix	1s
build for x86_64 with gcc	1s
build for x86_64 with llvm-16	2s
veristat	1s
test_progs on x86_64 with gcc	1s
test_progs_parallel on x86_64 with gcc	3s
test_progs_no_alu32 on x86_64 with gcc	1s
test_progs_no_alu32_parallel on x86_64 with gcc	1s
test_maps on x86_64 with gcc	1s
test_verifier on x86_64 with gcc	1s
test_progs on x86_64 with llvm-16	1s
test_progs_parallel on x86_64 with llvm-16	1s
test_progs_no_alu32 on x86_64 with llvm-16	2s
test_progs_no_alu32_parallel on x86_64 with llvm-16	1s
test_maps on x86_64 with llvm-16	2s
test_verifier on x86_64 with llvm-16	1s
	21s

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