Clang currently imports certain functions (like __imp__CxxThrowException) even when statically linking.
Whereas MSVC statically links them (like __CxxThrowException). In clang, function linkage is controlled via /MT
flag which is a clang-cl flag. This flag gets expanded to -flto-visibility-public-std which is a -cc1 option.
So from clang driver there is no way to statically link these functions. This patch makes -flto-visibility-public-std a
driver flag which can be used to control function linkage.