mac: Remove unused machine_os_build_major

We added this back when nacl couldn't be built on macOS 10.15.
Now that that works, we no longer use machine_os_build_major, so remove it.

Bug: 1049832,1147069
Change-Id: I5c52631cc3500e9cd0057d32ccba1b8da97bd8b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2536783
Commit-Queue: Nico Weber <thakis@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Auto-Submit: Nico Weber <thakis@chromium.org>
Reviewed-by: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827825}

build/config/mac/mac_sdk.gni

@@ -90,7 +90,6 @@ _mac_sdk_result = exec_script(script_name, sdk_info_args, "scope")
 xcode_version = _mac_sdk_result.xcode_version
 xcode_build = _mac_sdk_result.xcode_build
 machine_os_build = _mac_sdk_result.machine_os_build
-machine_os_build_major = _mac_sdk_result.machine_os_build_major
 if (mac_sdk_path == "" && use_system_xcode && ios_use_goma_rbe) {
   mac_sdk_path = _mac_sdk_result.sdk_path
 }

build/config/mac/sdk_info.py

@@ -41,6 +41,7 @@ def SplitVersion(version):
   version = version.split('.')
   return itertools.islice(itertools.chain(version, itertools.repeat('0')), 0, 3)
 
+
 def FormatVersion(version):
   """Converts Xcode version to a format required for DTXcode in Info.plist
 
@@ -54,6 +55,7 @@ def FormatVersion(version):
   major, minor, patch = SplitVersion(version)
   return ('%2s%s%s' % (major, minor, patch)).replace(' ', '0')
 
+
 def FillXcodeVersion(settings, developer_dir):
   """Fills the Xcode version and build number into |settings|."""
   if developer_dir:
@@ -79,21 +81,6 @@ def FillMachineOSBuild(settings):
                                               ]).decode('UTF-8').strip()
   settings['machine_os_build'] = machine_os_build
 
-  # The reported build number is made up from the kernel major version number,
-  # a minor version represented as a letter, a build number, and an optional
-  # packaging version.
-  #
-  # For example, the macOS 10.15.3 GM build is 19D76.
-  # - 19 is the Darwin kernel that ships with 10.15.
-  # - D is minor version 4. 10.15.0 builds had minor version 1.
-  # - 76 is the build number. 75 other builds were stamped before GM came out.
-  #
-  # The macOS 10.15.4 beta 5 build is 19E258a. The trailing "a" means the same
-  # build output was packaged twice.
-  build_match = re.match(r'^(\d+)([A-Z])(\d+)([a-z]?)$', machine_os_build)
-  assert build_match, "Unexpected macOS build format: %r" % machine_os_build
-  settings['machine_os_build_major'] = int(build_match.group(1), 10)
-
 
 def FillSDKPathAndVersion(settings, platform, xcode_version):
   """Fills the SDK path and version for |platform| into |settings|."""