not working -- look at nix emscripten support first before further work

lib/spack/env/cc

@@ -241,14 +241,14 @@ case "$command" in
         mode=cpp
         debug_flags="-g"
         ;;
-    cc|c89|c99|gcc|clang|armclang|icc|icx|pgcc|nvc|xlc|xlc_r|fcc|amdclang|cl.exe)
+    cc|c89|c99|gcc|clang|armclang|icc|icx|pgcc|nvc|xlc|xlc_r|fcc|amdclang|cl.exe|emcc)
         command="$SPACK_CC"
         language="C"
         comp="CC"
         lang_flags=C
         debug_flags="-g"
         ;;
-    c++|CC|g++|clang++|armclang++|icpc|icpx|dpcpp|pgc++|nvc++|xlc++|xlc++_r|FCC|amdclang++)
+    c++|CC|g++|clang++|armclang++|icpc|icpx|dpcpp|pgc++|nvc++|xlc++|xlc++_r|FCC|amdclang++|em++)
         command="$SPACK_CXX"
         language="C++"
         comp="CXX"

lib/spack/env/emscripten/em++

@@ -0,0 +1 @@
+../cc

lib/spack/env/emscripten/emcc

@@ -0,0 +1 @@
+../cc

lib/spack/spack/compilers/emscripten.py

@@ -15,8 +15,8 @@ class Emscripten(Compiler):
     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++'),
+    link_paths = {'cc': os.path.join('emscripten', 'emcc'),
+                  'cxx': os.path.join('emscripten', 'em++'),
                   'f77': '',
                   'fc': ''}
 
@@ -31,3 +31,7 @@ def debug_flags(self):
     @property
     def opt_flags(self):
         return ['-O0', '-O1', '-O2', '-O3', '-Os', '-Oz']
+
+    @property
+    def disable_new_dtags(self):
+        return ''