Cherry-pick 271986@main (f365728). rdar://119615600

    [build-webkit] Add --architecture argument
    https://bugs.webkit.org/show_bug.cgi?id=266342
    rdar://119615600

    Reviewed by Ryan Haddad.

    Add a '--architecture' argument to 'build-webkit' which allows
    the caller to override the architecutre used by 'build-webkit',
    and appropriately sets 'ONLY_ACTIVE_ARCH=NO' if '--architecture'
    is specified.

    * Tools/Scripts/build-webkit: Add documentation of '--architecture' option.
    * Tools/Scripts/webkitdirs.pm:
    (determineArchitecture): Parse the '--architecture' option and set didUserSpecifyArchitecture.
    (XcodeOptions): Set ONLY_ACTIVE_ARCH=NO if '--architecutre' was passed.

    Canonical link: https://commits.webkit.org/271986@main

Canonical link: https://commits.webkit.org/267815.629@safari-7617-branch

Tools/Scripts/build-webkit

@@ -115,6 +115,7 @@ Usage: $programName [options] [options to pass to build system]
   --debug                           Compile with Debug configuration
   --release                         Compile with Release configuration
   --sdk=<sdk>                       Use a specific Xcode SDK (Apple platforms only)
+  --arch=<architecture>             Compile for a specific architecture (or architectures)
   --ios-device                      Use "iphoneos.internal" SDK if installed, else "iphoneos" SDK (iOS only)
   --device                          DEPRECATED alias of --ios-device
   --ios-simulator                   Use "iphonesimulator.internal" SDK if installed, else "iphonesimulator" SDK (iOS only)

Tools/Scripts/webkitdirs.pm

@@ -245,6 +245,7 @@ use constant IOS_DEVELOPMENT_CERTIFICATE_NAME_PREFIX => "iPhone Developer: ";
 our @EXPORT_OK;
 
 my $architecture;
+my $didUserSpecifyArchitecture = 0;
 my %nativeArchitectureMap = ();
 my $asanIsEnabled;
 my $tsanIsEnabled;
@@ -539,6 +540,13 @@ sub determineArchitecture
     return if defined $architecture;
 
     determineBaseProductDir();
+
+    # The user explicitly specified the architecture, don't assume anything
+    if (checkForArgumentAndRemoveFromARGVGettingValue("--architecture", \$architecture)) {
+        $didUserSpecifyArchitecture = 1;
+        return;
+    }
+
     $architecture = nativeArchitecture([]);
     if (isAppleCocoaWebKit() && $architecture eq "arm64") {
         determineXcodeSDK();
@@ -1259,6 +1267,7 @@ sub XcodeOptions
     push @options, "WK_LTO_MODE=$ltoMode" if $ltoMode;
     push @options, @baseProductDirOption;
     push @options, "ARCHS=$architecture" if $architecture;
+    push @options, "ONLY_ACTIVE_ARCH=NO" if $didUserSpecifyArchitecture;
     push @options, "SDKROOT=$xcodeSDK" if $xcodeSDK;
     if (xcodeVersion() lt "15.0") {
         push @options, "TAPI_USE_SRCROOT=YES" if $ENV{UseSRCROOTSupportForTAPI};