[build] allow user to override the default number of build jobs (#1255)

User could issue SONIC_BUILD_JOBS=<num> to set number of concurrent
build job(s) to run.

With this commit, the default setting is still left at 1.

Author: yxieca

Makefile

@@ -13,6 +13,7 @@
 #  * PASSWORD: Desired password -- default at rules/config
 #  * KEEP_SLAVE_ON: Keeps slave container up after building-process concludes.
 #  * SOURCE_FOLDER: host path to be mount as /var/src, only effective when KEEP_SLAVE_ON=yes
+#  * SONIC_BUILD_JOB: Specifying number of concurrent build job(s) to run
 #
 ###############################################################################
 
@@ -59,7 +60,8 @@ SONIC_BUILD_INSTRUCTION :=  make \
                            SHUTDOWN_BGP_ON_START=$(SHUTDOWN_BGP_ON_START) \
                            ENABLE_SYNCD_RPC=$(ENABLE_SYNCD_RPC) \
                            PASSWORD=$(PASSWORD) \
-                           USERNAME=$(USERNAME)
+                           USERNAME=$(USERNAME) \
+                           SONIC_BUILD_JOBS=$(SONIC_BUILD_JOBS)
 
 .PHONY: sonic-slave-build sonic-slave-bash init
 

slave.mk

@@ -74,7 +74,11 @@ ifeq ($(PASSWORD),)
 override PASSWORD := $(DEFAULT_PASSWORD)
 endif
 
-MAKEFLAGS += -j $(SONIC_CONFIG_BUILD_JOBS)
+ifeq ($(SONIC_BUILD_JOBS),)
+override SONIC_BUILD_JOBS := $(SONIC_CONFIG_BUILD_JOBS)
+endif
+
+MAKEFLAGS += -j $(SONIC_BUILD_JOBS)
 export SONIC_CONFIG_MAKE_JOBS
 
 ###############################################################################
@@ -86,7 +90,7 @@ $(info )
 $(info Build Configuration)
 $(info "CONFIGURED_PLATFORM"             : "$(if $(PLATFORM),$(PLATFORM),$(CONFIGURED_PLATFORM))")
 $(info "SONIC_CONFIG_PRINT_DEPENDENCIES" : "$(SONIC_CONFIG_PRINT_DEPENDENCIES)")
-$(info "SONIC_CONFIG_BUILD_JOBS"         : "$(SONIC_CONFIG_BUILD_JOBS)")
+$(info "SONIC_BUILD_JOBS"                : "$(SONIC_BUILD_JOBS)")
 $(info "SONIC_CONFIG_MAKE_JOBS"          : "$(SONIC_CONFIG_MAKE_JOBS)")
 $(info "DEFAULT_USERNAME"                : "$(DEFAULT_USERNAME)")
 $(info "DEFAULT_PASSWORD"                : "$(DEFAULT_PASSWORD)")