Allow running under Rosetta 2 if build_arch=x86_64

This allows users who explicitly request it by setting build_arch in
macports.conf to have a fully x86_64 build environment.

src/macports1.0/macports.tcl

@@ -1069,14 +1069,6 @@ proc mportinit {{up_ui_options {}} {up_options {}} {up_variations {}}} {
         }
     }
 
-    # Check that the current platform is the one we were configured for, otherwise need to do migration
-    set skip_migration_check [expr {[info exists macports::global_options(ports_no_migration_check)] && $macports::global_options(ports_no_migration_check)}]
-    if {!$skip_migration_check && [migrate::needs_migration migrate_reason]} {
-        ui_error $migrate_reason
-        ui_error "Please run 'sudo port migrate' or follow the migration instructions: https://trac.macports.org/wiki/Migration"
-        return -code error "OS platform mismatch"
-    }
-
     # Ensure that the macports user directory (i.e. ~/.macports) exists if HOME is defined.
     # Also save $HOME for later use before replacing it with our own.
     if {[info exists env(HOME)]} {
@@ -1614,6 +1606,14 @@ match macports.conf.default."
         set build_arch [lindex $build_arch 0]
     }
 
+    # Check that the current platform is the one we were configured for, otherwise need to do migration
+    set skip_migration_check [expr {[info exists macports::global_options(ports_no_migration_check)] && $macports::global_options(ports_no_migration_check)}]
+    if {!$skip_migration_check && [migrate::needs_migration migrate_reason]} {
+        ui_error $migrate_reason
+        ui_error "Please run 'sudo port migrate' or follow the migration instructions: https://trac.macports.org/wiki/Migration"
+        return -code error "OS platform mismatch"
+    }
+
     if {![info exists macosx_deployment_target]} {
         if {[vercmp $macos_version 11] >= 0} {
             set macosx_deployment_target ${macos_version_major}.0

src/macports1.0/migrate.tcl

@@ -234,7 +234,7 @@ namespace eval migrate {
     #
     # @return true iff the migration procedure is needed
     proc needs_migration {{reasonvar {}}} {
-        global macports::os_platform macports::os_major
+        global macports::os_platform macports::os_major macports::build_arch
         if {$reasonvar ne {}} {
             upvar $reasonvar reason
             set reason {}
@@ -245,7 +245,7 @@ namespace eval migrate {
             set reason "Current platform \"$os_platform $os_major\" does not match expected platform \"$macports::autoconf::os_platform $macports::autoconf::os_major\""
             return 1
         }
-        if {$os_platform eq "darwin" && $os_major >= 20
+        if {$os_platform eq "darwin" && $os_major >= 20 && $build_arch ne "x86_64"
                 && ![catch {sysctl sysctl.proc_translated} translated] && $translated
         } then {
             # Check if our tclsh has an arm64 slice - rebuilding not needed if it's universal

src/macports1.0/selfupdate.tcl

@@ -414,6 +414,7 @@ proc selfupdate::verify_signature_legacy {path signature_path} {
 # @param source Path to the source code to be installed.
 proc selfupdate::install {source} {
     global \
+        macports::build_arch \
         macports::developer_dir \
         macports::macos_version_major \
         macports::os_major \
@@ -489,7 +490,7 @@ proc selfupdate::install {source} {
                 }
             }
         }
-        if {$os_major >= 20 && ![catch {sysctl sysctl.proc_translated} translated] && $translated} {
+        if {$os_major >= 20 && $build_arch ne "x86_64" && ![catch {sysctl sysctl.proc_translated} translated] && $translated} {
             # Force a native build
             set arch_arg "/usr/bin/arch -arm64 /usr/bin/env "
         }