packages/exim: enable parallel make

Parallel make used to be broken in exim, as reported in its docs. Now that
line has disappeared from the docs, and parallel make is actually working.

Tested with 'make exim-dirclean ; time make BR2_JLEVEL=999 exim': builds
still succeed and the build time decreases from 34 to 11 seconds on my
host.

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Cc: Bernd Kuhls <bernd.kuhls@t-online.de>
Tested-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit 153b78ee2640938db328edb64e6c40e064154957)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/exim/exim.mk

@@ -120,16 +120,14 @@ endif
 
 # We need the host version of macro_predef during the build, before
 # building it we need to prepare the makefile.
-# "The -j (parallel) flag must not be used with make"
-# (http://www.exim.org/exim-html-current/doc/html/spec_html/ch04.html)
 define EXIM_BUILD_CMDS
-	$(TARGET_MAKE_ENV) build=br $(MAKE1) -C $(@D) makefile
-	$(HOST_MAKE_ENV) $(MAKE1) -C $(@D)/build-br macro_predef \
+	$(TARGET_MAKE_ENV) build=br $(MAKE) -C $(@D) makefile
+	$(HOST_MAKE_ENV) $(MAKE) -C $(@D)/build-br macro_predef \
 		CC=$(HOSTCC) \
 		LNCC=$(HOSTCC) \
 		CFLAGS="-std=c99 $(HOST_CFLAGS)" \
 		LFLAGS="-fPIC $(HOST_LDFLAGS)"
-	$(TARGET_MAKE_ENV) build=br $(MAKE1) -C $(@D) $(EXIM_STATIC_FLAGS) \
+	$(TARGET_MAKE_ENV) build=br $(MAKE) -C $(@D) $(EXIM_STATIC_FLAGS) \
 		CFLAGS="-std=c99 $(TARGET_CFLAGS)"
 endef
 
@@ -137,7 +135,7 @@ endef
 # something when installing...
 define EXIM_INSTALL_TARGET_CMDS
 	DESTDIR=$(TARGET_DIR) INSTALL_ARG="-no_chown -no_symlink" build=br \
-	  $(MAKE1) -C $(@D) $(EXIM_STATIC_FLAGS) \
+	  $(MAKE) -C $(@D) $(EXIM_STATIC_FLAGS) \
 		CFLAGS="-std=c99 $(TARGET_CFLAGS)" \
 		install
 	chmod u+s $(TARGET_DIR)/usr/sbin/exim