GN Build fixes for Flutter + gen_snapshot fix

runtime/platform/globals.h

Index: runtime/platform/globals.h
diff --git a/runtime/platform/globals.h b/runtime/platform/globals.h
index 40c4b07a47aef7d4047ecf750e2cac4265bc543e..a0dfdd07e0245cd39d2a6cd03259a8c32a2b45a0 100644
--- a/runtime/platform/globals.h
+++ b/runtime/platform/globals.h
@@ -2,8 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-#ifndef PLATFORM_GLOBALS_H_
-#define PLATFORM_GLOBALS_H_
+#ifndef RUNTIME_PLATFORM_GLOBALS_H_
+#define RUNTIME_PLATFORM_GLOBALS_H_
 
 // __STDC_FORMAT_MACROS has to be defined before including <inttypes.h> to
 // enable platform independent printf format specifiers.
@@ -136,6 +136,10 @@
 #endif  // defined(PRODUCT)
 
 
+#if defined(DART_PRECOMPILED_RUNTIME) && defined(DART_PRECOMPILER)
+#error DART_PRECOMPILED_RUNTIME and DART_PRECOMPILER are mutually exclusive
+#endif  // defined(DART_PRECOMPILED_RUNTIME) && defined(DART_PRECOMPILER)
+
 namespace dart {
 
 struct simd128_value_t {
@@ -674,4 +678,4 @@ static inline T ReadUnaligned(const T* ptr) {
 
 }  // namespace dart
 
-#endif  // PLATFORM_GLOBALS_H_
+#endif  // RUNTIME_PLATFORM_GLOBALS_H_