Fix building when $(CC_STAGE0) contains spaces

Spotted by Bill Tutt

rules/distdir-opts.mk

@@ -79,8 +79,8 @@ $1_$2_HSC2HS_LD_OPTS:=$$(shell for i in $$($1_$2_DIST_LD_OPTS); do echo \'--lfla
 endif
 
 $1_$2_ALL_HSC2HS_OPTS = \
- --cc=$$(CC_STAGE$3) \
- --ld=$$(CC_STAGE$3) \
+ '--cc=$$(CC_STAGE$3)' \
+ '--ld=$$(CC_STAGE$3)' \
  $$(CONF_HSC2HS_OPTS) \
  $$(SRC_HSC2HS_OPTS) \
  $$(SRC_HSC2HS_OPTS_STAGE$3) \