[Support] Fix building on FreeBSD and OpenBSD (llvm#127005)

Fix building after a6f7cb5.

Check for the function getauxval() instead of just the sys/auxv.h
header.

Author: brad0

llvm/cmake/config-ix.cmake

@@ -21,7 +21,6 @@ if (ANDROID OR CYGWIN OR CMAKE_SYSTEM_NAME MATCHES "AIX|DragonFly|FreeBSD|Haiku|
   set(HAVE_MACH_MACH_H 0)
   set(HAVE_MALLOC_MALLOC_H 0)
   set(HAVE_PTHREAD_H 1)
-  set(HAVE_SYS_AUXV_H 1)
   set(HAVE_SYS_MMAN_H 1)
   set(HAVE_SYSEXITS_H 1)
   set(HAVE_UNISTD_H 1)
@@ -53,7 +52,6 @@ else()
   check_include_file(mach/mach.h HAVE_MACH_MACH_H)
   check_include_file(malloc/malloc.h HAVE_MALLOC_MALLOC_H)
   check_include_file(pthread.h HAVE_PTHREAD_H)
-  check_include_file(sys/auxv.h HAVE_SYS_AUXV_H)
   check_include_file(sys/mman.h HAVE_SYS_MMAN_H)
   check_include_file(sysexits.h HAVE_SYSEXITS_H)
   check_include_file(unistd.h HAVE_UNISTD_H)
@@ -321,6 +319,7 @@ check_symbol_exists(getrusage sys/resource.h HAVE_GETRUSAGE)
 check_symbol_exists(isatty unistd.h HAVE_ISATTY)
 check_symbol_exists(futimens sys/stat.h HAVE_FUTIMENS)
 check_symbol_exists(futimes sys/time.h HAVE_FUTIMES)
+check_symbol_exists(getauxval sys/auxv.h HAVE_GETAUXVAL)
 # AddressSanitizer conflicts with lib/Support/Unix/Signals.inc
 # Avoid sigaltstack on Apple platforms, where backtrace() cannot handle it
 # (rdar://7089625) and _Unwind_Backtrace is unusable because it cannot unwind

llvm/include/llvm/Config/config.h.cmake

@@ -295,6 +295,6 @@
 
 #cmakedefine HAVE_BUILTIN_THREAD_POINTER ${HAVE_BUILTIN_THREAD_POINTER}
 
-#cmakedefine HAVE_SYS_AUXV_H ${HAVE_SYS_AUXV_H}
+#cmakedefine HAVE_GETAUXVAL ${HAVE_GETAUXVAL}
 
 #endif

llvm/lib/Support/Unix/Process.inc

@@ -31,7 +31,7 @@
 #ifdef HAVE_MALLOC_MALLOC_H
 #include <malloc/malloc.h>
 #endif
-#ifdef HAVE_SYS_AUXV_H
+#ifdef HAVE_GETAUXVAL
 #include <sys/auxv.h>
 #endif
 
@@ -66,7 +66,7 @@ Process::Pid Process::getProcessId() {
 // On Cygwin, getpagesize() returns 64k(AllocationGranularity) and
 // offset in mmap(3) should be aligned to the AllocationGranularity.
 Expected<unsigned> Process::getPageSize() {
-#if defined(HAVE_SYS_AUXV_H)
+#if defined(HAVE_GETAUXVAL)
   static const int page_size = ::getauxval(AT_PAGESZ);
 #elif defined(HAVE_GETPAGESIZE)
   static const int page_size = ::getpagesize();