Bazel client: fix broken compilation 

Do not include <windows.h> in file_platform.h
because it #defines many symbols that later code,
particularly function definitions, conflict with,
e.g. GetUserName, SendMessage.

This was breaking the Bazel bootstrap project on
CI.

--
Change-Id: Ie4b59b00fc617bd3e7d0cbb967c1232798e055de
Reviewed-on: https://cr.bazel.build/9127
PiperOrigin-RevId: 148986922
MOS_MIGRATED_REVID=148986922

src/main/cpp/blaze_util_windows.cc

diff --git a/src/main/cpp/blaze_util_windows.cc b/src/main/cpp/blaze_util_windows.cc
index 839490b..a862fda 100644
--- a/src/main/cpp/blaze_util_windows.cc
+++ b/src/main/cpp/blaze_util_windows.cc
@@ -1274,6 +1274,12 @@
 #endif  // COMPILER_MSVC
 }
 
+#ifdef GetUserName
+// By including <windows.h>, we have GetUserName defined either as
+// GetUserNameA or GetUserNameW.
+#undef GetUserName
+#endif
+
 string GetUserName() {
   WCHAR buffer[UNLEN + 1];
   DWORD len = UNLEN + 1;