cross compile for armv7 with musl error for stacktrace_generic-inl.inc used

when use bazel cross compile for armv7 with musl libc library, meet below errors, use stacktrace_arm-inl.inc by manual change stacktrace_config.h compile success, why stacktrace_config.h not detect armv7 then use stacktrace_arm-inl.inc?

```
ERROR: /root/src/cpp/abseil-cpp/absl/debugging/BUILD.bazel:30:11: Compiling absl/debugging/stacktrace.cc failed: (Exit 1): arm-openwrt-linux-muslgnueabi-gcc failed: error executing command external/gcc11_arm_armv7_none_musleabi/bin/arm-openwrt-linux-muslgnueabi-gcc -fPIC -fstack-protector -Wall -fno-omit-frame-pointer '--sysroot=external/gcc11_arm_armv7_none_musleabi' -pthread ... (remaining 37 arguments skipped)

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
arm-openwrt-linux-muslgnueabi-gcc: warning: environment variable 'STAGING_DIR' not defined
In file included from ./absl/debugging/internal/stacktrace_generic-inl.inc:23,
from absl/debugging/stacktrace.cc:46:
/usr/include/execinfo.h:23:1: error: '__BEGIN_DECLS' does not name a type
23 | __BEGIN_DECLS
| ^~~~~~~~~~~~~
/usr/include/execinfo.h:33:6: error: expected initializer before '__THROW'
33 | __THROW __nonnull ((1));
| ^~~~~~~
/usr/include/execinfo.h:39:6: error: expected initializer before '__THROW'
39 | __THROW __nonnull ((1));
| ^~~~~~~
/usr/include/execinfo.h:41:1: error: '__END_DECLS' does not name a type
41 | __END_DECLS
| ^~~~~~~~~~~
In file included from ./absl/debugging/internal/stacktrace_generic-inl.inc:25,
from absl/debugging/stacktrace.cc:46:
external/gcc11_arm_armv7_none_musleabi/bin/../lib/gcc/arm-openwrt-linux-muslgnueabi/11.2.0/../../../../arm-openwrt-linux-muslgnueabi/include/c++/11.2.0/cstring:77:11: error: 'memchr' has not been declared in '::'
77 | using ::memchr;

```