[GR-16925] Show stacktrace for errors in BuildInformationProcessor.

PullRequest: truffleruby/929

Author: eregon

src/processor/java/org/truffleruby/processor/BuildInformationProcessor.java

@@ -59,7 +59,7 @@ public synchronized void init(ProcessingEnvironment env) {
             revision = runCommand("git rev-parse --short=8 HEAD");
             compileDate = runCommand("git log -1 --date=short --pretty=format:%cd");
         } catch (Throwable e) {
-            env.getMessager().printMessage(Kind.ERROR, e.getClass() + " " + e.getMessage());
+            throw new Error(e);
         }
     }
 
@@ -80,13 +80,20 @@ private File findHome() throws URISyntaxException {
         return source.getParentFile();
     }
 
-    private String runCommand(String command) throws IOException {
+    private String runCommand(String command) throws IOException, InterruptedException {
         final Process git = new ProcessBuilder(command.split("\\s+"))
                         .directory(trufflerubyHome)
                         .start();
+        final String firstLine;
         try (BufferedReader reader = new BufferedReader(new InputStreamReader(git.getInputStream()))) {
-            return reader.readLine();
+            firstLine = reader.readLine();
         }
+
+        final int exitCode = git.waitFor();
+        if (exitCode != 0) {
+            throw new Error("Command " + command + " failed with exit code " + exitCode);
+        }
+        return firstLine;
     }
 
     @Override