print error messages from glslang

it's quite annoying otherwise, the build would fail with no explanation

Force-Push: yes
Change-Id: Ia5405c1f0e63f778da49ca1c85139f5e785fde29

1 files changed, 11 insertions, 8 deletions

diff --git a/build.rs b/build.rs
index dde9a94..b4ffa72 100644
--- a/build.rs
+++ b/build.rs
@@ -31,15 +31,18 @@ fn process_all () -> std::io::Result<()> {
                   .join(format!("{}.spv",
                         input_path.file_name().unwrap().to_str().unwrap()));
 
-    if !Command::new("glslang")
-           .arg("-V")
-           .arg(&input_path)
-           .arg("-o")
-           .arg(output_path)
-           .status()?.success()
-    {
-      println!("cargo::error=Failed to compile shader {}",
+    let result = Command::new("glslang")
+            .arg("-V")
+            .arg(&input_path)
+            .arg("-o")
+            .arg(output_path)
+            .output()?;
+    if !result.status.success() {
+      println!("cargo::error=Failed to compile shader {}; details follow.",
                input_path.display());
+      for line in std::str::from_utf8(&result.stdout).unwrap().lines() {
+        println!("cargo::error={}", line);
+      }
     }
 
     println!("cargo::rerun-if-changed={}", input_path.display());