gdb: Do not set musl specific CFLAGS

These settings are no longer needed because we define gl_cv_func_gettimeofday_clobber=no already and stat issue is alrwady fixed via [1]

[1] https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=3c025cfe5efc44eb4dfb03b53dca28e75096dd1e

---
 meta/recipes-devtools/gdb/gdb_8.3.bb | 1 -
 1 file changed, 1 deletion(-)

index c6eac84dd8..d70757a151 100644
@@ -26,4 +26,3 @@ EOF
 		chmod +x ${WORKDIR}/python
 	fi
 }
-CPPFLAGS_append_libc-musl = " -Drpl_gettimeofday=gettimeofday -Drpl_stat=stat"

2.22.0