Make ie4uinit.exe execution optional (#1240)

* - do not execute ie4uinit if it is not available
use 'where' to check if an executable is on the PATH

* Add log message informing the user an old application icon may still be cached

src/main/java/com/gluonhq/substrate/target/WindowsTargetConfiguration.java

@@ -285,6 +285,10 @@ private void createIconResource() throws InterruptedException, IOException {
     // During development if user changes the application icon, the same is not reflected immediately in Explorer.
     // To fix this, a cache clearance of the Windows explorer is required.
     private void clearExplorerCache() throws IOException, InterruptedException {
+        if (!executableOnPath("ie4uinit.exe")) {
+            Logger.logInfo("The application icon cache could not be cleared. As a result, the icon may not have been updated properly.");
+            return;
+        }
         ProcessRunner clearCache = new ProcessRunner("ie4uinit");
         clearCache.addArg(findCacheFlag());
         clearCache.runProcess("Clear Explorer cache");
@@ -311,6 +315,26 @@ private String findCacheFlag() throws IOException, InterruptedException {
         return flag;
     }
 
+    /**
+     * Returns whether the passed executable is available on the PATH.
+     * For best result, the extension should be included in the executable, as "foo" will return true for "foo.bat".
+     * But running "foo" in a ProcessBuilder will look for "foo.exe" and fail to run.
+     *
+     * @param executable name of the executable to check
+     * @return true if the executable is available on the PATH.
+     */
+    private boolean executableOnPath(String executable) {
+        try {
+            ProcessRunner whereProcess = new ProcessRunner("cmd.exe", "/c", "where", "/q", executable);
+            whereProcess.showSevereMessage(false);
+            int exit = whereProcess.runProcess("find executable");
+            return exit == 0;
+        } catch (IOException | InterruptedException e) {
+            Logger.logInfo(String.format("Unable to validate if %s is available on the PATH, assuming it is not.", executable));
+            return false;
+        }
+    }
+
     @Override
     List<String> getAdditionalSourceFiles() {
         if (projectConfiguration.isSharedLibrary()) {