set GHA runner max heap size dynamically based upon runner hardware

Before this change, we set the max heap size based upon runner OS.
That worked well enough, since we only used the free GitHub-hosted runners with well-known hardware.

Now that we have two different Ubuntu runner sizes, that older strategy is leaving free memory on the table.

Author: RBusarow

.github/actions/gradle-args/action.yml

@@ -21,25 +21,40 @@ runs:
       run: |
         runnerOS=$RUNNER_OS
 
-        # Set common JVM arguments
-        jvmArgs="-XX:+HeapDumpOnOutOfMemoryError -Dfile.encoding=UTF-8"
+        totalMemory=0
+        # How much memory does the OS require? 
+        memoryOverhead=0
 
         case $runnerOS in
           macOS)
-            jvmArgs="-Xmx10g -XX:MaxMetaspaceSize=5g $jvmArgs"
+            totalMemory=$(sysctl -n hw.memsize | awk '{print int($1/1024/1024/1024+0.5)}')
+            memoryOverhead=3
             ;;
           Linux)
-            jvmArgs="-Xmx4g -XX:MaxMetaspaceSize=3g $jvmArgs"
+            totalMemory=$(awk '/MemTotal/ {print int($2/1024/1024+0.5)}' /proc/meminfo)
+            memoryOverhead=3
             ;;
           Windows)
-            jvmArgs="-Xmx3g -XX:MaxMetaspaceSize=756m $jvmArgs"
+            # Fetch and parse memory in MB, then convert to GB
+            totalMemory=$(powershell -Command "& { [Math]::Round((Get-CimInstance Win32_ComputerSystem).TotalPhysicalMemory / 1GB) }")
+
+            # Check if totalMemory is a valid number
+            if ! [[ "$totalMemory" =~ ^[0-9]+$ ]]; then
+              echo "Failed to retrieve or parse total memory: $totalMemory"
+              exit 1
+            fi
+            memoryOverhead=3
             ;;
           *)
             echo "Unsupported runner OS: $runnerOS"
             exit 1
             ;;
         esac
 
+        availableMemory=$((totalMemory - memoryOverhead))
+
+        jvmArgs="-Xmx${availableMemory}g -XX:+HeapDumpOnOutOfMemoryError -Dfile.encoding=UTF-8"
+
         propertyArgs="-Dorg.gradle.daemon=false -Dkotlin.compiler.execution.strategy=in-process -Dkotlin.incremental=false"
 
         echo "gradle-property-args=$propertyArgs" >> $GITHUB_OUTPUT