gn build: Don't assume valgrind.h exists on Linux

[hans]

Summary

It didn't on my machine, so defaulting it to off seems better.

[thakis]

Thanks!

llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn

94

since this is now set unconditionally, can you put it in this block of unconditionally set things?

[hans]

Will do.

llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn

values = [
     "HAVE_FFI_FFI_H=",
     "HAVE_FFI_H=",
     "HAVE_LIBPFM=",
     "HAVE_LIBPSAPI=",
     "HAVE_MALLCTL=",
     "HAVE_SIGNAL_H=1",
     "HAVE_STRERROR=1",
     "HAVE_SYS_STAT_H=1",
     "HAVE_SYS_TYPES_H=1",
     "HAVE__ALLOCA=",
     "HAVE___ALLOCA=",
     "HAVE___ASHLDI3=",
     "HAVE___ASHRDI3=",
     "HAVE___CHKSTK=",
     "HAVE___CHKSTK_MS=",
     "HAVE___CMPDI2=",
     "HAVE___DIVDI3=",
values += [
       "HAVE_MALLINFO=",
       "HAVE_POSIX_FALLOCATE=",
       "HAVE_SCHED_GETAFFINITY=",
       "HAVE_CPU_COUNT=",
       "HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC=",
     ]
   }
 
-  if (current_os == "linux") {
-    values += [ "HAVE_VALGRIND_VALGRIND_H=1" ]
-  } else {
-    values += [ "HAVE_VALGRIND_VALGRIND_H=" ]
-  }
+  # Even Linux systems often don't have valgrind.h, so default it to off.
 
   if (current_os == "mac") {
     values += [
       "HAVE_CRASHREPORTER_INFO=1",
       "HAVE_DECL_ARC4RANDOM=1",
       "HAVE_DLADDR=1",
       "HAVE_MALLOC_H=",
       "HAVE_MACH_MACH_H=1",