git-gui: Ensure msgfmt failure stops GNU make

If we have a failure executing msgfmt (such as the process just
crashes no matter what arguments you supply it because its own
installation is borked) we should stop the build process rather
than letting it continue along its merry way as if the .msg files
were created.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>

Makefile

@@ -47,8 +47,8 @@ ifndef V
 	QUIET_GEN      = $(QUIET)echo '   ' GEN $@ &&
 	QUIET_BUILT_IN = $(QUIET)echo '   ' BUILTIN $@ &&
 	QUIET_INDEX    = $(QUIET)echo '   ' INDEX $(dir $@) &&
-	QUIET_MSGFMT0  = $(QUIET)printf '    MSGFMT %12s ' $@ &&
-	QUIET_MSGFMT1  = 2>&1 | sed -e 's/fuzzy translations/fuzzy/' | sed -e 's/ messages//g'
+	QUIET_MSGFMT0  = $(QUIET)printf '    MSGFMT %12s ' $@ && v=`
+	QUIET_MSGFMT1  = 2>&1` && echo "$$v" | sed -e 's/fuzzy translations/fuzzy/' | sed -e 's/ messages//g'
 	QUIET_2DEVNULL = 2>/dev/null
 
 	INSTALL_D0 = dir=