Fix build break for MSVC.

Introduce AROUT to control whether there is space between ARFLAGS and
$@.  This regression was introduced by
ad505e0ec6.

Reported by Mike Hommey.

Makefile.in

@@ -56,7 +56,7 @@ CTARGET = @CTARGET@
 LDTARGET = @LDTARGET@
 MKLIB = @MKLIB@
 AR = @AR@
-ARFLAGS = crus
+ARFLAGS = @ARFLAGS@
 CC_MM = @CC_MM@
 
 ifeq (macho, $(ABI))
@@ -187,7 +187,7 @@ $(objroot)lib/$(LIBJEMALLOC)_s.$(A) : $(COBJS)
 
 $(STATIC_LIBS):
 	@mkdir -p $(@D)
-	$(AR) $(ARFLAGS) $@ $+
+	$(AR) $(ARFLAGS)@AROUT@ $+
 
 $(objroot)test/bitmap$(EXE): $(objroot)src/bitmap.$(O)
 

configure.ac

@@ -226,6 +226,8 @@ PIC_CFLAGS='-fPIC -DPIC'
 CTARGET='-o $@'
 LDTARGET='-o $@'
 EXTRA_LDFLAGS=
+ARFLAGS='crus'
+AROUT=' $@'
 CC_MM=1
 
 AN_MAKEVAR([AR], [AC_PROG_AR])
@@ -316,6 +318,7 @@ case "${host}" in
 	  LDTARGET='-Fe$@'
 	  AR='lib'
 	  ARFLAGS='-nologo -out:'
+	  AROUT='$@'
 	  CC_MM=
         else
 	  importlib="${so}"
@@ -348,6 +351,8 @@ AC_SUBST([PIC_CFLAGS])
 AC_SUBST([CTARGET])
 AC_SUBST([LDTARGET])
 AC_SUBST([MKLIB])
+AC_SUBST([ARFLAGS])
+AC_SUBST([AROUT])
 AC_SUBST([CC_MM])
 
 if test "x$abi" != "xpecoff"; then