lz4: don't build library and tools in parallel

Since commit e93fec6673e (lz4: bump to version 1.8.1.2) we use two make
targets, 'lib' and 'lz4'. Both targets depend on the static library.
When these targets run in parallel the two make instances that build the
static library race against each other. Split these targets to ensure
build order.

Should fix:
http://autobuild.buildroot.net/results/a8d/a8d956ff420f6a265c5c00b33646dbbc24ce2d48/

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/lz4/lz4.mk

@@ -15,7 +15,8 @@ LZ4_MAKE_OPTS += BUILD_SHARED=no
 endif
 
 define HOST_LZ4_BUILD_CMDS
-	$(HOST_MAKE_ENV) $(HOST_CONFIGURE_OPTS) $(MAKE) -C $(@D) lib lz4
+	$(HOST_MAKE_ENV) $(HOST_CONFIGURE_OPTS) $(MAKE) -C $(@D) lib
+	$(HOST_MAKE_ENV) $(HOST_CONFIGURE_OPTS) $(MAKE) -C $(@D) lz4
 endef
 
 define HOST_LZ4_INSTALL_CMDS
@@ -25,7 +26,9 @@ endef
 
 define LZ4_BUILD_CMDS
 	$(TARGET_MAKE_ENV) $(TARGET_CONFIGURE_OPTS) $(MAKE) $(LZ4_MAKE_OPTS) \
-		-C $(@D) lib lz4
+		-C $(@D) lib
+	$(TARGET_MAKE_ENV) $(TARGET_CONFIGURE_OPTS) $(MAKE) $(LZ4_MAKE_OPTS) \
+		-C $(@D) lz4
 endef
 
 define LZ4_INSTALL_STAGING_CMDS