fixup! config.mak.uname: add support for clangarm64

This commit introduced an `else ifeq` pattern that is arguably more
elegant than the previous pattern, so let's adjust the existing
conditional block, too.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

config.mak.uname

@@ -728,8 +728,7 @@ ifeq ($(uname_S),MINGW)
 		prefix = /mingw32
 		HOST_CPU = i686
 		BASIC_LDFLAGS += -Wl,--pic-executable,-e,_mainCRTStartup
-        endif
-        ifeq (MINGW64,$(MSYSTEM))
+        else ifeq (MINGW64,$(MSYSTEM))
 		prefix = /mingw64
 		HOST_CPU = x86_64
 		BASIC_LDFLAGS += -Wl,--pic-executable,-e,mainCRTStartup