This patch works around build issues in libsanitizer.  Note that we carry the
same patches for GCC since it includes the same libsanitizer.

Work around this build error on glibc 2.26:

  /tmp/guix-build-clang-runtime-3.5.2.drv-0/compiler-rt-3.5.2.src/lib/asan/asan_linux.cc: In function 'bool __asan::AsanInterceptsSignal(int)':
  /tmp/guix-build-clang-runtime-3.5.2.drv-0/compiler-rt-3.5.2.src/lib/asan/asan_linux.cc:224:20: error: 'SIGSEGV' was not declared in this scope

diff --git a/libsanitizer/asan/asan_linux.cc b/libsanitizer/asan/asan_linux.cc
index c504168..59087b9 100644
--- a/lib/asan/asan_linux.cc
+++ b/lib/asan/asan_linux.cc
@@ -29,6 +29,7 @@
 #include <dlfcn.h>
 #include <fcntl.h>
 #include <pthread.h>
+#include <signal.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <unwind.h>

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Now, work around this other error:

  /tmp/guix-build-clang-runtime-3.5.2.drv-0/compiler-rt-3.5.2.src/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc: In function 'int __sanitizer::TracerThread(void*)':
  /tmp/guix-build-clang-runtime-3.5.2.drv-0/compiler-rt-3.5.2.src/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc:239:22: error: aggregate 'sigaltstack handler_stack' has incomplete type and cannot be defined


diff --git a/lib/sanitizer_common/sanitizer_linux.cc b/lib/sanitizer_common/sanitizer_linux.cc
index 2cefa20..223d9c6 100644
--- a/lib/sanitizer_common/sanitizer_linux.cc
+++ b/lib/sanitizer_common/sanitizer_linux.cc
@@ -546,8 +546,7 @@ uptr internal_prctl(int option, uptr arg2, uptr arg3, uptr arg4, uptr arg5) {
 }
 #endif
 
-uptr internal_sigaltstack(const struct sigaltstack *ss,
-                         struct sigaltstack *oss) {
+uptr internal_sigaltstack(const void *ss, void *oss) {
   return internal_syscall(SYSCALL(sigaltstack), (uptr)ss, (uptr)oss);
 }
 
diff --git a/lib/sanitizer_common/sanitizer_linux.h b/lib/sanitizer_common/sanitizer_linux.h
index 4497702..1594058 100644
--- a/lib/sanitizer_common/sanitizer_linux.h
+++ b/lib/sanitizer_common/sanitizer_linux.h
@@ -19,7 +19,6 @@
 #include "sanitizer_platform_limits_posix.h"
 
 struct link_map;  // Opaque type returned by dlopen().
-struct sigaltstack;
 
 namespace __sanitizer {
 // Dirent structure for getdents(). Note that this structure is different from
@@ -28,8 +27,7 @@ struct linux_dirent;
 
 // Syscall wrappers.
 uptr internal_getdents(fd_t fd, struct linux_dirent *dirp, unsigned int count);
-uptr internal_sigaltstack(const struct sigaltstack* ss,
-                          struct sigaltstack* oss);
+uptr internal_sigaltstack(const void* ss, void* oss);
 uptr internal_sigprocmask(int how, __sanitizer_sigset_t *set,
     __sanitizer_sigset_t *oldset);
 void internal_sigfillset(__sanitizer_sigset_t *set);
diff --git a/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc b/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
index c919e4f..014162af 100644
--- a/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
+++ b/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
@@ -267,7 +267,7 @@ static int TracerThread(void* argument) {
 
   // Alternate stack for signal handling.
   InternalScopedBuffer<char> handler_stack_memory(kHandlerStackSize);
-  struct sigaltstack handler_stack;
+  stack_t handler_stack;
   internal_memset(&handler_stack, 0, sizeof(handler_stack));
   handler_stack.ss_sp = handler_stack_memory.data();
   handler_stack.ss_size = kHandlerStackSize;
diff --git a/lib/tsan/tsan_platform_linux.cc b/lib/tsan/tsan_platform_linux.cc
index 09cec5f..908f4fe 100644
--- a/lib/tsan/rtl/tsan_platform_linux.cc
+++ b/lib/tsan/rtl/tsan_platform_linux.cc
@@ -291,7 +291,7 @@ bool IsGlobalVar(uptr addr) {
 int ExtractResolvFDs(void *state, int *fds, int nfd) {
 #if SANITIZER_LINUX
   int cnt = 0;
-  __res_state *statp = (__res_state*)state;
+  struct __res_state *statp = (struct __res_state*)state;
   for (int i = 0; i < MAXNS && cnt < nfd; i++) {
     if (statp->_u._ext.nsaddrs[i] && statp->_u._ext.nssocks[i] != -1)
       fds[cnt++] = statp->_u._ext.nssocks[i];
-- 
2.9.3