Fix conda build failure due to long prefix on Mac.

Build extension module with sufficient header space for
install_name_tool and for enormous prefix lengths used in conda build.

Author: pavoljuhas

SConstruct

@@ -110,6 +110,7 @@ if env['PLATFORM'] == 'darwin':
     env.Replace(SHLINKFLAGS=darwin_shlinkflags)
     env.AppendUnique(SHLINKFLAGS=['-bundle'])
     env.AppendUnique(SHLINKFLAGS=['-undefined', 'dynamic_lookup'])
+    env.AppendUnique(SHLINKFLAGS=['-headerpad_max_install_names'])
     fast_linkflags[:] = []
 
 # Compiler specific options