Remove unneeded VC4 flags.

Thanks to Stephen Walker <sdwalker@myrealbox.com> for the patch.
Bug #255616 r=cls

jpeg/Makefile.in

@@ -102,17 +102,3 @@ endif
 FORCE_STATIC_LIB = 1
 
 include $(topsrcdir)/config/rules.mk
-
-ifeq ($(OS_ARCH),WINNT)
-ifndef GNU_CC
-#//  -Zi -GM needed to compile mmx functions in assembly.
-CFLAGS	+= -Zi -GM
-endif
-endif
-
-# Using the -Zi flag causes debugging info to be written to the .pdb files,
-# so we cannot do parallel builds here
-ifeq ($(OS_ARCH),WINNT)
-.NOTPARALLEL::
-endif
-