CompileTest: Add Directives to Ignore arm-unknown-* Tests

Author: veera-sivarajan

Diff for: src/tools/compiletest/src/directive-list.rs

@@ -39,6 +39,10 @@ const KNOWN_DIRECTIVE_NAMES: &[&str] = &[
     "ignore-android",
     "ignore-apple",
     "ignore-arm",
+    "ignore-arm-unknown-linux-gnueabi",
+    "ignore-arm-unknown-linux-gnueabihf",
+    "ignore-arm-unknown-linux-musleabi",
+    "ignore-arm-unknown-linux-musleabihf",
     "ignore-avr",
     "ignore-beta",
     "ignore-cdb",