Allow GoogleTest to Test STATIC Functions

> This is a cherry-pick to keep the  -D GOOGLETEST_HOST_UNIT_TEST_BUILD=1

Cmocka is able to test STATIC functions by including the C file
in the test file. However, in many scenarios, GoogleTest files
cannot do this as the C++ compiler has stricter rules than the
C compiler.

This patch updates the UnitTestFrameworkPkgHost.dsc.in to add
a new build flag GOOGLETEST_HOST_UNIT_TEST_BUILD for
HOST_APPLICATIONS only. Base.h is then updated to undef STATIC
if this flag is set. This allows for STATIC functions to be tested
in GoogleTest.

There is less danger of symbol collision here, because HOST_APPLICATIONS
are running with the least amount of dependencies possible. This still
allows for interfaces tests (where a Library Class is tested, not an
instance, so the library is linked in to the test instead of compiled)
as the library in this case will not be compiled as a HOST_APPLICATION
and so the STATIC functions will remain STATIC.

UnitTestFrameworkPkg/UnitTestFrameworkPkgHost.dsc.inc

@@ -43,7 +43,9 @@
   #
   # MSFT
   #
-  MSFT:*_*_*_CC_FLAGS               = /EHsc
+  # MU_CHANGE [BEGIN] - Allow GoogleTest to Test STATIC Functions
+  MSFT:*_*_*_CC_FLAGS               = /EHsc -D GOOGLETEST_HOST_UNIT_TEST_BUILD=1
+  # MU_CHANGE [END] - Allow GoogleTest to Test STATIC Functions
   MSFT:*_*_*_DLINK_FLAGS            == /out:"$(BIN_DIR)\$(MODULE_NAME_GUID).exe" /pdb:"$(BIN_DIR)\$(MODULE_NAME_GUID).pdb" /IGNORE:4001 /NOLOGO /SUBSYSTEM:CONSOLE /DEBUG /STACK:0x40000,0x40000 /WHOLEARCHIVE
   MSFT:*_*_IA32_DLINK_FLAGS         = /MACHINE:I386
   MSFT:*_*_X64_DLINK_FLAGS          = /MACHINE:AMD64