Move internal_uname to #if SANITIZER_LINUX scope.

[marxin]

Summary

Remove it from target-specific scope which corresponds
to sanitizer_linux.cpp where it lives in the same macro
scope.

It's a correction of:
https://reviews.llvm.org/D76776

[marxin]

It fixes multilib build in GCC on ppc64 after libsanitizer merge.

[eugenis]

LGTM

[marxin]

Merged to master as b638b63b99d66786cb37336292604a2ae3490cfd.

compiler-rt/lib/sanitizer_common/sanitizer_linux.h

 // internal_sigaction instead.
 int internal_sigaction_norestorer(int signum, const void *act, void *oldact);
 void internal_sigdelset(__sanitizer_sigset_t *set, int signum);
 #if defined(__x86_64__) || defined(__mips__) || defined(__aarch64__) \
   || defined(__powerpc64__) || defined(__s390__) || defined(__i386__) \
   || defined(__arm__)
 uptr internal_clone(int (*fn)(void *), void *child_stack, int flags, void *arg,
                     int *parent_tidptr, void *newtls, int *child_tidptr);
-int internal_uname(struct utsname *buf);
 #endif
+int internal_uname(struct utsname *buf);
 #elif SANITIZER_FREEBSD
 void internal_sigdelset(__sanitizer_sigset_t *set, int signum);
 #elif SANITIZER_NETBSD
 void internal_sigdelset(__sanitizer_sigset_t *set, int signum);
 uptr internal_clone(int (*fn)(void *), void *child_stack, int flags, void *arg);
 #endif  // SANITIZER_LINUX
 
 // This class reads thread IDs from /proc/<pid>/task using only syscalls.