build.py: inherit environment in the gcc builder

[labath]

Summary

This should enable the compiler to find the system linker for the link
step.

[labath]

Stella, could you please try whether this solves the problem you reported in D55430? I think this should do the trick, but I can't be sure because (for whatever reason), things seem to work for me even without this patch.

[stella.stamenova]

This does fix the issues. Thanks!

lit/helper/build.py

 
 def format_text(lines, indent_0, indent_n):
     result = ' ' * indent_0 + lines[0]
     for next in lines[1:]:
         result = result + '\n{0}{1}'.format(' ' * indent_n, next)
     return result
 
 def print_environment(env):
+    if env is None:
+        print('    Inherited')
+        return
     for e in env:
         value = env[e]
         lines = value.split(os.pathsep)
         formatted_value = format_text(lines, 0, 7 + len(e))
         print('    {0} = {1}'.format(e, formatted_value))
 
 def find_executable(binary_name, search_paths):
     if sys.platform == 'win32':
def _get_compilation_command(self, source, obj):
         if self.nodefaultlib:
             args.append('-nostdinc')
             args.append('-static')
         args.append('-c')
 
         args.extend(['-o', obj])
         args.append(source)
 
-        return ('compiling', [source], obj, {}, args)
+        return ('compiling', [source], obj, None, args)
 
     def _get_link_command(self):
         args = []
         args.append(self.compiler)
         args.append('-m' + self.arch)
         if self.nodefaultlib:
             args.append('-nostdlib')
             args.append('-static')
             main_symbol = 'main'
             if sys.platform == 'darwin':
                 main_symbol = '_main'
             args.append('-Wl,-e,' + main_symbol)
         args.extend(['-o', self._exe_file_name()])
         args.extend(self._obj_file_names())
 
-        return ('linking', self._obj_file_names(), self._exe_file_name(), {}, args)
+        return ('linking', self._obj_file_names(), self._exe_file_name(), None, args)
 
 
     def output_files(self):
         outputs = []
         if self.mode == 'compile' or self.mode == 'compile-and-link':
             outputs.extend(self._obj_file_names())
         if self.mode == 'link' or self.mode == 'compile-and-link':
             outputs.append(self._exe_file_name())