add emscripten compiler emcc, which can't compile executables (yet!)

lib/spack/spack/compilers/emcc.py

@@ -0,0 +1,33 @@
+# Copyright 2013-2022 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+import os
+import re
+
+import spack.compiler
+from spack.version import ver
+
+
+class Emcc(spack.compiler.Compiler):
+    cc_names = ['emcc']
+    cxx_names = ['em++']
+
+    # Named wrapper links within build_env_path
+    link_paths = {'cc': os.path.join('upstream', 'emscripten', 'emcc'),
+                  'cxx': os.path.join('upstream', 'emscripten', 'em++'),
+                  'f77': '',
+                  'fc': ''}
+
+    @property
+    def verbose_flag(self):
+        return "-v"
+
+    @property
+    def debug_flags(self):
+        return ['-g', '-gsource-map', '-gseparate-dwarf', '-g0', '-g1', '-g2', '-g3']
+
+    @property
+    def opt_flags(self):
+        return ['-O0', '-O1', '-O2', '-O3', '-Os', '-Oz']