[msan] Fix compilation on non-glibc

SANITIZER_GLIBC is always defined so should be tested with an if not an
ifdef.

Fixes: ad7e250

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D159041

Author: brooksdavis

compiler-rt/lib/msan/msan_interceptors.cpp

@@ -1767,7 +1767,7 @@ void InitializeInterceptors() {
   INTERCEPT_STRTO(wcstoul);
   INTERCEPT_STRTO(wcstoll);
   INTERCEPT_STRTO(wcstoull);
-#ifdef SANITIZER_GLIBC
+#if SANITIZER_GLIBC
   INTERCEPT_STRTO(__isoc23_strtod);
   INTERCEPT_STRTO(__isoc23_strtof);
   INTERCEPT_STRTO(__isoc23_strtold);