Bug 1484190 - Unblock MSVC 2017 15.8. r=dmajor

--HG--
extra : rebase_source : b21ef13181d447cbbd822f073c80d982dd212dc4
extra : source : 5d24aab5c5a18b18edfd13cf786e94c545e36e94

build/moz.configure/toolchain.configure

@@ -933,19 +933,19 @@ def compiler(language, host_or_target, c_compiler=None, other_compiler=None,
                 raise FatalCheckError(
                     'This version (%s) of the MSVC compiler is not '
                     'supported.\n'
-                    'You must install Visual C++ 2017 Update 6 in '
-                    'order to build.\n'
+                    'You must install Visual C++ 2017 Update 6 or '
+                    'Update 8 or later in order to build.\n'
                     'See https://developer.mozilla.org/en/'
                     'Windows_Build_Prerequisites' % info.version)
 
             # MSVC version 15.7 and the previews for 15.8, at least,
             # can't build Firefox.
-            if info.version >= '19.14.0':
+            if info.version >= '19.14.0' and info.version < '19.15.0':
                 raise FatalCheckError(
                     'This version (%s) of the MSVC compiler is not '
                     'supported due to compiler bugs.\n'
-                    'You must install Visual C++ 2017 Update 6 in '
-                    'order to build.\n'
+                    'You must install Visual C++ 2017 Update 6 or '
+                    'Update 8 or later in order to build.\n'
                     'See https://developer.mozilla.org/en/'
                     'Windows_Build_Prerequisites' % info.version)