[libc] Clean up Windows macros

This clean-up removes checks for _WIN64, as the _WIN32 macro returns 1
whenever the compilation targe is 32- or 64-bit ARM.

Reviewed By: aeubanks

Differential Revision: https://reviews.llvm.org/D106706

libc/utils/FPUtil/PlatformDefs.h

@@ -13,7 +13,7 @@
 #define X87_FPU
 #endif
 
-#if defined(_WIN32) || defined(_WIN64)
+#if defined(_WIN32)
 #define LONG_DOUBLE_IS_DOUBLE
 #endif
 

libc/utils/FPUtil/TestHelpers.cpp

@@ -74,7 +74,7 @@ template void describeValue<double>(const char *, double,
 template void describeValue<long double>(const char *, long double,
                                          testutils::StreamWrapper &);
 
-#if defined(_WIN32) || defined(_WIN64)
+#if defined(_WIN32)
 #define sigjmp_buf jmp_buf
 #define sigsetjmp(buf, save) setjmp(buf)
 #define siglongjmp(buf, val) longjmp(buf, val)

libc/utils/UnitTest/PlatformDefs.h

@@ -9,7 +9,7 @@
 #ifndef LLVM_LIBC_UTILS_UNITTEST_PLATFORMDEFS_H
 #define LLVM_LIBC_UTILS_UNITTEST_PLATFORMDEFS_H
 
-#if !(defined(_WIN32) || defined(_WIN64))
+#if !defined(_WIN32)
 #define ENABLE_SUBPROCESS_TESTS
 #endif