Fix passing /DEBUG:FASTLINK linker option

...which needs to be past at the end of the command line, after a /link option.
Looks like at least MSVC 2015 Update 3 silently ignores the garbage /D option
-DEBUG:fastlink, while clang-cl complains.

Fixes 96af392ba4 "Use /debug:fastlink linker
option to improve link performance".

Change-Id: Ib679d4ce3ac4a7622ba7b066edbfe1872892137a
Reviewed-on: https://gerrit.libreoffice.org/35048
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: David Ostrovsky <david@ostrovsky.org>

solenv/gbuild/platform/com_MSC_class.mk

@@ -57,7 +57,8 @@ $(call gb_Helper_abbreviate_dirs,\
 		$(INCLUDE) \
 		$(if $(filter YES,$(CXXOBJECT_X64)), -U_X86_ -D_AMD64_,) \
 		-c $(3) \
-		-Fo$(1)) $(call gb_create_deps,$(4),$(1),$(3))
+		-Fo$(1)) $(if $(filter $(true),$(gb_SYMBOL)),/link /DEBUG:FASTLINK) \
+		$(call gb_create_deps,$(4),$(1),$(3))
 endef
 
 # PrecompiledHeader class

solenv/gbuild/platform/com_MSC_defs.mk

@@ -250,7 +250,6 @@ gb_LinkTarget_LDFLAGS += \
 gb_DEBUGINFO_FLAGS := \
 	-FS \
 	-Zi \
-	-DEBUG:fastlink \
 
 gb_DEBUG_CFLAGS :=