Workaround broken constexpr in MSVC

Summary: `constexpr` is known to be broken in MSVC causing errors when using format string compilation so disable `FMT_COMPILE` there.

Reviewed By: neildhar

Differential Revision: D26019769

fbshipit-source-id: b823b24d4e73fcf9632f8e648ebb9a4e73c43bb1

folly/CompiledFormat.h

@@ -24,6 +24,11 @@
 #undef FMT_COMPILE
 #endif
 
+#ifdef _MSC_VER
+// Workaround broken constexpr in MSVC.
+#undef FMT_COMPILE
+#endif
+
 // Fallback to runtime format string processing for compatibility with fmt 6.x.
 #ifndef FMT_COMPILE
 #define FMT_COMPILE(format_str) format_str