Improve Java detection, fix OSX warning

Some OSX versions were opening a dialog if Java was not installed,
because we tested Java in $PATH, which is a stub that just opens
a warning dialog telling you to install Java. We now avoid doing
that on OSX. Based on the logic from Flutter:
https://github.com/flutter/flutter/blob/026ee9756cbbf574fdb7fde1f420813ee340a5c0/packages/flutter_tools/lib/src/android/android_sdk.dart\#L408-L445

Author: pimterry

src/interceptors/jvm.ts

@@ -15,11 +15,20 @@ type JvmTarget = { pid: string, name: string, interceptedByProxy: number | undef
 const javaBinPromise: Promise<string | false> = (async () => {
     // Check what Java binaries might exist:
     const javaBinPaths = [
-        await getMacJavaHome(), // Magic Mac helper for exactly this
-        !!process.env.JAVA_HOME && // $JAVA_HOME/bin/java is standard
+        // $JAVA_HOME/bin/java is the way to explicitly configure this
+        !!process.env.JAVA_HOME &&
             path.join(process.env.JAVA_HOME!!, 'bin', 'java'),
-        (await commandExists('java')) && // Fallback to java in $PATH
+
+        // Magic Mac helper for exactly this, used if available
+        await getMacJavaHome(),
+
+        // Fallback to $PATH, but not on Mac, where by default this is a "Install Java" dialog warning
+        (await commandExists('java')) && process.platform !== "darwin" &&
             'java'
+
+        // In future, we could improve this by also finding & using the JVM from Android Studio. See
+        // Flutter's implementation of logic required to do this:
+        // https://github.com/flutter/flutter/blob/master/packages/flutter_tools/lib/src/android/android_studio.dart
     ].filter(p => !!p) as string[];
 
     // Run a self test in parallel with each of them: