Use correct environment for REGEN in VS backend.

Try to guess which VS Command Prompt was used for the Meson call.
If one is chosen invoke it before calling Meson in REGEN command.

mesonbuild/backend/vs2010backend.py

@@ -189,6 +189,33 @@ def generate_regen_info(self):
         with open(filename, 'wb') as f:
             pickle.dump(regeninfo, f)
 
+    def get_vcvars_command(self):
+        has_arch_values = 'VSCMD_ARG_TGT_ARCH' in os.environ and 'VSCMD_ARG_HOST_ARCH' in os.environ
+
+        # Use vcvarsall.bat if we found it.
+        if 'VCINSTALLDIR' in os.environ:
+            vs_version = os.environ['VisualStudioVersion'] \
+                if 'VisualStudioVersion' in os.environ else None
+            relative_path = 'Auxiliary\\Build\\' if vs_version == '15.0' else ''
+            script_path = os.environ['VCINSTALLDIR'] + relative_path + 'vcvarsall.bat'
+            if os.path.exists(script_path):
+                if has_arch_values:
+                    target_arch = os.environ['VSCMD_ARG_TGT_ARCH']
+                    host_arch = os.environ['VSCMD_ARG_HOST_ARCH']
+                else:
+                    target_arch = os.environ.get('Platform', 'x86')
+                    host_arch = target_arch
+                arch = host_arch + '_' + target_arch if host_arch != target_arch else target_arch
+                return '"%s" %s' % (script_path, arch)
+
+        # Otherwise try the VS2017 Developer Command Prompt.
+        if 'VS150COMNTOOLS' in os.environ and has_arch_values:
+            script_path = os.environ['VS150COMNTOOLS'] + 'VsDevCmd.bat'
+            if os.path.exists(script_path):
+                return '"%s" -arch=%s -host_arch=%s' % \
+                    (script_path, os.environ['VSCMD_ARG_TGT_ARCH'], os.environ['VSCMD_ARG_HOST_ARCH'])
+        return ''
+
     def get_obj_target_deps(self, obj_list):
         result = {}
         for o in obj_list:
@@ -1096,7 +1123,7 @@ def gen_vcxproj(self, target, ofname, guid):
         elif targetplatform == 'arm':
             targetmachine.text = 'MachineARM'
         else:
-            raise MesonException('Unsupported Visual Studio target machine: ' + targetmachine)
+            raise MesonException('Unsupported Visual Studio target machine: ' + targetplatform)
 
         meson_file_group = ET.SubElement(root, 'ItemGroup')
         ET.SubElement(meson_file_group, 'None', Include=os.path.join(proj_to_src_dir, build_filename))
@@ -1213,7 +1240,9 @@ def gen_regenproj(self, project_name, ofname):
         ET.SubElement(midl, 'ProxyFileName').text = '%(Filename)_p.c'
         regen_command = self.environment.get_build_command() + ['--internal', 'regencheck']
         private_dir = self.environment.get_scratch_dir()
+        vcvars_command = self.get_vcvars_command()
         cmd_templ = '''setlocal
+call %s > NUL
 "%s" "%s"
 if %%errorlevel%% neq 0 goto :cmEnd
 :cmEnd
@@ -1231,7 +1260,7 @@ def gen_regenproj(self, project_name, ofname):
         message = ET.SubElement(custombuild, 'Message')
         message.text = 'Checking whether solution needs to be regenerated.'
         ET.SubElement(custombuild, 'Command').text = cmd_templ % \
-            ('" "'.join(regen_command), private_dir)
+            (vcvars_command, '" "'.join(regen_command), private_dir)
         ET.SubElement(custombuild, 'Outputs').text = Vs2010Backend.get_regen_stampfile(self.environment.get_build_dir())
         deps = self.get_regen_filelist()
         ET.SubElement(custombuild, 'AdditionalInputs').text = ';'.join(deps)

mesonbuild/environment.py

@@ -188,6 +188,9 @@ def detect_windows_arch(compilers):
                 platform = os.environ.get('BUILD_PLAT', 'x86')
                 if platform == 'Win32':
                     return 'x86'
+            elif 'VSCMD_ARG_TGT_ARCH' in os.environ:
+                # On MSVC 2017 'Platform' is not set in VsDevCmd.bat
+                return os.environ['VSCMD_ARG_TGT_ARCH']
             else:
                 # On MSVC 2010 and later 'Platform' is only set when the
                 # target arch is not 'x86'.  It's 'x64' when targeting