Fix shared libraries in autoconf projects on Linux host

Partial revert of commit 53a969d, plus addition of comment
explaining why the verbiage about ld compatibility is there.

Added a check for the 'GNU' token in 'emcc -v' output to tests.

AUTHORS

@@ -193,3 +193,4 @@ a license to everyone to use it as detailed in LICENSE.)
 * Tim Guan-tin Chien <timdream@gmail.com>
 * Krzysztof Jakubowski <nadult@fastmail.fm>
 * Vladimír Vondruš <mosra@centrum.cz>
+* Brion Vibber <brion@pobox.com>

emcc

@@ -172,7 +172,8 @@ There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR P
   exit(0)
 
 elif len(sys.argv) == 2 and sys.argv[1] == '-v': # -v with no inputs
-  print 'emcc (Emscripten gcc/clang-like replacement) %s' % shared.EMSCRIPTEN_VERSION
+  # autoconf likes to see 'GNU' in the output to enable shared object support
+  print 'emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) %s' % shared.EMSCRIPTEN_VERSION
   code = subprocess.call([shared.CLANG, '-v'])
   shared.check_sanity(force=True)
   exit(code)

tests/test_other.py

@@ -22,6 +22,7 @@ def test_emcc(self):
       # -v, without input files
       output = Popen([PYTHON, compiler, '-v'], stdout=PIPE, stderr=PIPE).communicate()
       self.assertContained('''clang version''', output[1].replace('\r', ''), output[1].replace('\r', ''))
+      self.assertContained('''GNU''', output[0])
 
       # --help
       output = Popen([PYTHON, compiler, '--help'], stdout=PIPE, stderr=PIPE).communicate()