Use -Wno-cpp to avoid errors on #warning

[ret2libc]

Your checklist for this pull request

• I've read the guidelines for contributing to this repository
• I made sure to follow the project's coding style
• I've added tests that prove my fix is effective or that my feature works (if possible)
• I've updated the documentation and the radare2 book with the relevant information (if needed)

Detailed description

See #17781 (comment) . I've seen this option in https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html .

Test plan

Everything should be green, capstone included.

[XVilka]

Good. Still needs to fix one more:

gcc -Ilibr/asm/8a8d21f@@r_asm@sha -I. -I../ -I../libr/include -Ilibr/asm/../../shlr -I../libr/asm/../../shlr -I../libr/asm/arch/include -I../libr/asm/arch -I../libr/asm/arch/h8300 -I../libr/asm/arch/hexagon -I../libr/asm/arch/msp430 -I../libr/asm/arch/rsp -I../libr/asm/arch/mcore -I../libr/asm/arch/v850 -I../libr/asm/arch/propeller -I../libr/asm/arch/ebc -I../libr/asm/arch/cr16 -I../libr/asm/arch/8051 -I../libr/asm/arch/v810 -I../libr/asm/arch/or1k -I../shlr/spp -I../shlr/sdb/src -I../shlr/zip/zlib -I../shlr/capstone/include -I../shlr/java -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -g -fvisibility=hidden -Werror -Wno-cpp -fPIC -pthread -DR2_PLUGIN_INCORE=1 -MD -MQ 'libr/asm/8a8d21f@@r_asm@sha/p_asm_tms320.c.o' -MF 'libr/asm/8a8d21f@@r_asm@sha/p_asm_tms320.c.o.d' -o 'libr/asm/8a8d21f@@r_asm@sha/p_asm_tms320.c.o' -c ../libr/asm/p/asm_tms320.c
../libr/asm/p/asm_tms320.c:15:12: error: ‘cd’ defined but not used [-Werror=unused-variable]
 static csh cd = 0;
            ^~
cc1: all warnings being treated as errors