add test for wasm linker override=clang

Author: reez12g

Diff for: tests/run-make/wasm-override-linker/Makefile

@@ -0,0 +1,11 @@
+include ../tools.mk
+
+ifeq ($(TARGET),wasm32-unknown-unknown)
+all:
+	$(RUSTC) foo.rs --crate-type cdylib --target $(TARGET) -C linker=$(CLANG)
+else ifeq ($(TARGET),wasm64-unknown-unknown)
+all:
+	$(RUSTC) foo.rs --crate-type cdylib --target $(TARGET) -C linker=$(CLANG)
+else
+all:
+endif

Diff for: tests/run-make/wasm-override-linker/foo.rs

@@ -0,0 +1,6 @@
+#![crate_type = "cdylib"]
+
+#[no_mangle]
+pub extern "C" fn add(a: i32, b: i32) -> i32 {
+    a + b
+}