Verify wasmkit is a universal binary (#163)

* In lit.cfg, add wasmkit_path and substitution; check that path exists

* New test-universal-darwin.py verifies wasmkit executable is universal

- Test runs only on Darwin
- Check compares output of 'file' tool (exists on macOS and Linux)
- Similar test could verify other executables (but need BOM list?)

Author: wti

lit.cfg

@@ -207,6 +207,11 @@ docc_path = lit_config.params.get(
     os.path.join(package_path, "usr", "bin", "docc"))
 lit_config.note("testing using 'docc': {}".format(docc_path))
 
+wasmkit_path = lit_config.params.get(
+    "wasmkit",
+    os.path.join(package_path, "usr", "bin", "wasmkit"))
+lit_config.note("testing using 'wasmkit': {}".format(wasmkit_path))
+
 # Verify they exist.
 if not os.path.exists(swift_path):
     lit_config.fatal("swift does not exist!")
@@ -231,6 +236,8 @@ else:
 
 if not os.path.exists(docc_path):
     lit_config.fatal("docc does not exist!")
+if not os.path.exists(wasmkit_path):
+    lit_config.fatal("wasmkit does not exist!")
 
 # Define our supported substitutions.
 config.substitutions.append( ('%{package_path}', package_path) )
@@ -246,6 +253,7 @@ config.substitutions.append( ('%{readelf}', readelf_path) )
 config.substitutions.append( ('%{readobj}', readobj_path) )
 config.substitutions.append( ('%{sourcekit-lsp}', sourcekit_lsp_path) )
 config.substitutions.append( ('%{docc}', docc_path) )
+config.substitutions.append( ('%{wasmkit}', wasmkit_path) )
 
 # Add substitutions for swiftpm executables.
 swiftpm_build = lit_config.params.get("swiftpm-build")

test-snapshot-binaries/test-universal-darwin.py

@@ -0,0 +1,7 @@
+# Tests that executables are universal binaries on MacOS
+# REQUIRES: platform=Darwin
+#
+# RUN: file %{wasmkit} | %{FileCheck} --check-prefix CHECK-WASMKIT %s
+# CHECK-WASMKIT: {{.*}} Mach-O universal binary {{.*}}
+#
+