Add source build option to makefile

Makefile

@@ -1,5 +1,5 @@
 export TZ = UTC # same as Github
-export JAVA_HOME=/Library/Java/JavaVirtualMachines/zulu-11.jdk/Contents/Home
+export JAVA_HOME ?= /Library/Java/JavaVirtualMachines/zulu-11.jdk/Contents/Home
 
 MVN_OPTS = -Dmaven.javadoc.skip=true -Dmaven.test.skip=true -Dspotbugs.skip=true
 
@@ -10,6 +10,14 @@ default: tool/target/gp.jar
 tool/target/gp.jar: $(SOURCES)
 	./mvnw $(MVN_OPTS) package
 
+srcbuild:
+	# override the version, which would be "unsupported" without a git checkout
+ifdef GPPRO_VERSION
+	mkdir -p ./library/target/classes/pro/javacard/gp
+	echo "git.commit.id.describe=$(GPPRO_VERSION)" > ./library/target/classes/pro/javacard/gp/git.properties
+endif
+	./mvnw $(MVN_OPTS) -Dmaven.gitcommitid.skip=true package
+
 dep: $(SOURCES)
 	./mvnw $(MVN_OPTS) install