Limit memory inside GitHub Actions

Makefile

@@ -29,6 +29,14 @@ else
     log_and_or_display = > $(1) 2>&1
 endif
 
+ifdef GITHUB_ACTIONS
+    # Limit Java heap size inside GitHub Actions to 6G
+    JVM_MEM = "-Xms6g -Xmx6g"
+else
+    # If not specified, limit Java heap size ~32G
+    JVM_MEM ?= "-Xmx32736m -Xmx32736m"
+endif
+
 
 # Default recipe: route and score all given download-benchmarks
 .PHONY: run-$(ROUTER)
@@ -65,7 +73,7 @@ fpga-interchange-schema/interchange/capnp/java.capnp:
 # When inside GitHub Actions (which has no access to Vivado), and also when the routed netlist
 # was successfully converted back into a DCP, then return a mock PASS result
 %_$(ROUTER).check: %.netlist %_$(ROUTER).phys | compile-java
-	( ( (_JAVA_OPTIONS="-Xms6g -Xmx6g" ./gradlew -Dmain=com.xilinx.fpga24_routing_contest.CheckPhysNetlist :run --args='$^' $(call log_and_or_display,$@.log)) && echo "PASS" ) || echo "FAIL") > $@
+	( ( (GRADLE_OPTS="-Xms6g -Xmx6g" ./gradlew -Dmain=com.xilinx.fpga24_routing_contest.CheckPhysNetlist :run --args='$^' $(call log_and_or_display,$@.log)) && echo "PASS" ) || echo "FAIL") > $@
 	[ -z "${GITHUB_ACTION}" ] || [ ! -f "$(patsubst %.check,%.dcp,$@)" ] || echo "PASS" > $@
 
 .PHONY: score-$(ROUTER)
@@ -86,12 +94,11 @@ distclean: clean
 #### BEGIN ROUTER RECIPES
 
 ## RWROUTE
-# _JAVA_OPTIONS="-Xms32736m -Xmx32736m" sets the initial and maximum heap size of the JVM to be ~32GB
 # /usr/bin/time is used to measure the wall clock time
 # Gradle is used to invoke the PartialRouterPhysNetlist class' main method with arguments
 # $< (%_unrouted.phys) and $@ (%_rwroute.phys), and log_and_or_displaying all output into %_rwroute.phys.log
 %_rwroute.phys: %_unrouted.phys | compile-java
-	(_JAVA_OPTIONS="-Xms6g -Xmx6g" /usr/bin/time ./gradlew -Dmain=com.xilinx.fpga24_routing_contest.PartialRouterPhysNetlist :run --args='$< $@') $(call log_and_or_display,$@.log)
+	(GRADLE_OPTS="$(JVM_MEM)" /usr/bin/time ./gradlew -Dmain=com.xilinx.fpga24_routing_contest.PartialRouterPhysNetlist :run --args='$< $@') $(call log_and_or_display,$@.log)
 
 ## NXROUTE-POC
 %_nxroute-poc.phys: %_unrouted.phys xcvu3p.device | nxroute-deps fpga-interchange-schema/interchange/capnp/java.capnp