[sanitizer] Don't include <linux/user.h> in sanitizer_stoptheworld_linux_libcdep.cc on ARM Android.

[m.ostapenko]

Summary

Turned out that adding defined(arm) in sanitizer_stoptheworld_linux_libcdep.cc breaks android arm with some toolchains.

.../llvm/projects/compiler-rt/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc:36:11: fatal error:
      'linux/user.h' file not found
# include <linux/user.h>  // for pt_regs
          ^
1 error generated.

Context:
#if SANITIZER_ANDROID && defined(__arm__)
# include <linux/user.h>  // for pt_regs
#else

This patch removes corresponding #if SANITIZER_ANDROID && defined(__arm__) and a bit rearranges adjacent сode.
I don't have Android ARM target, so Kostya, could you help me in testing?

[cryptoad]

Works for me on my Android ARM & AArch64 testbeds.

[eugenis]

LGTM
works for me, too

compiler-rt/trunk/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc

 #include <errno.h>
 #include <sched.h> // for CLONE_* definitions
 #include <stddef.h>
 #include <sys/prctl.h> // for PR_* definitions
 #include <sys/ptrace.h> // for PTRACE_* definitions
 #include <sys/types.h> // for pid_t
 #include <sys/uio.h> // for iovec
 #include <elf.h> // for NT_PRSTATUS
-#if SANITIZER_ANDROID && defined(__arm__)
-# include <linux/user.h>  // for pt_regs
-#else
-# ifdef __aarch64__
+#if defined(__aarch64__) && !SANITIZER_ANDROID
 // GLIBC 2.20+ sys/user does not include asm/ptrace.h
-#  include <asm/ptrace.h>
-# endif
-# include <sys/user.h>  // for user_regs_struct
-# if SANITIZER_ANDROID && SANITIZER_MIPS
-#   include <asm/reg.h>  // for mips SP register in sys/user.h
-# endif
-#endif
+# include <asm/ptrace.h>
+#endif
+#include <sys/user.h>  // for user_regs_struct
+#if SANITIZER_ANDROID && SANITIZER_MIPS
+# include <asm/reg.h>  // for mips SP register in sys/user.h
+#endif
 #include <sys/wait.h> // for signal-related stuff
 
 #ifdef sa_handler
 # undef sa_handler
 #endif
 
 #ifdef sa_sigaction
 # undef sa_sigaction