improve Python packaging

python/MANIFEST.in

@@ -1,5 +1,3 @@
-include include/olm/olm.h
-include include/olm/pk.h
-include include/olm/sas.h
+include include/olm/*.h
 include Makefile
 include olm_build.py

python/olm_build.py

@@ -31,13 +31,6 @@ link_args = ["-L../build"]
 if DEVELOP and DEVELOP.lower() in ["yes", "true", "1"]:
     link_args.append('-Wl,-rpath=../build')
 
-# If libolm is compiled statically, we may need to link to the C++ standard
-# library dynamically.  This flag allows passing the required linker flag to do
-# so.
-CXX_LIB = os.environ.get("CXX_LIB")
-if CXX_LIB:
-    link_args.extend(CXX_LIB.split())
-
 headers_build = subprocess.Popen("make headers", shell=True)
 headers_build.wait()
 
@@ -52,7 +45,9 @@ ffibuilder.set_source(
     """,
     libraries=["olm"],
     extra_compile_args=compile_args,
-    extra_link_args=link_args)
+    extra_link_args=link_args,
+    source_extension=".cpp", # we need to link the C++ standard library, so use a C++ extension
+)
 
 with open(os.path.join(PATH, "include/olm/error.h")) as f:
     ffibuilder.cdef(f.read(), override=True)