[libc] remove extra -Werror (#78761)

-Werror is now a global default as of
commit c52b467 ("Reapply "[libc] build with -Werror (#73966)"
(#74506)")

Author: nickdesaulniers

libc/src/signal/linux/CMakeLists.txt

@@ -41,7 +41,6 @@ add_object_library(
     -fomit-frame-pointer
     -O3
     -Wframe-larger-than=0
-    -Werror
     -Wno-attributes
     # asan creates asan.module_ctor which uses stack space, causing warnings.
     -fno-sanitize=address