--- lib/critcl/Config.in.orig
+++ lib/critcl/Config.in
@@ -81,20 +81,31 @@ threadflags     -DUSE_THREAD_ALLOC=1 -D_REENTRANT=1 -D_THREAD_SAFE=1    \
 # OSX - check if universal binaries supported by the installed toolchain
 
 if {[string match macosx-* $platform]} {
+    if {[info exists ::env(osxmin)] && $::env(osxmin) ne ""} {
+        set osxmin $::env(osxmin)
+    } elseif {[info exists ::env(MACOSX_DEPLOYMENT_TARGET)] && $::env(MACOSX_DEPLOYMENT_TARGET) ne ""} {
+        set osxmin $::env(MACOSX_DEPLOYMENT_TARGET)
+    }
     if {[info exists ::env(SDKROOT)] && $::env(SDKROOT) ne ""} {
         set SDKROOT $::env(SDKROOT)
+    } elseif {![catch {exec xcrun --show-sdk-path} sdkpath] && $sdkpath ne {} && [file exists $sdkpath]} {
+        set SDKROOT $sdkpath
     } else {
         # look for an SDK supporting universal binaries
+        set SDKROOT  ""
         set pos [string length MacOSX]
 	set sdklist {}
-	set base /Developer
-	catch {set base [exec xcode-select -print-path]}
+	set bases {/Library/Developer/CommandLineTools /Developer}
+	catch {lappend bases [exec xcode-select -print-path]}
+	foreach base $bases {
         foreach dir [glob -nocomplain -tails \
 			    -directory $base/SDKs MacOSX*] {
             set ver [string trimright \
                         [file rootname [string range $dir $pos end]] u]
-            if {"$ver" != "" && [package vcompare $ver 10.4] >= 0}  {
-                # 10.4 is earliest supporting universal that we support
+            if {"$ver" != "" && [package vcompare $ver 10.4] >= 0
+                && (![info exists osxmin] || [package vcompare $ver $osxmin] >= 0)}  {
+                # 10.4 is earliest supporting universal that we support, and
+                # the deployment target cannot be newer than the SDK.
                 set path($ver) $dir
                 lappend sdklist $ver
             }
@@ -102,16 +113,21 @@ if {[string match macosx-* $platform]} {
         if {[llength $sdklist]} {
             set ver [lindex [lsort -command "package vcompare" $sdklist] 0]
             set SDKROOT $base/SDKs/$path($ver)
-        } else {
-            set SDKROOT  ""
+            break
         }
     }
+    }
+    if {![info exists osxmin]} {
     if {$SDKROOT ne ""} {
         # get the SDKsettings for the min OSX value supported
 	set info ""
-        if [catch {
+	if {[catch {
+	        set osxmin [exec plutil -extract DefaultProperties.MACOSX_DEPLOYMENT_TARGET \
+	                        raw $SDKROOT/SDKSettings.plist]
+	}]} {
+        if {[catch {
                 set info [exec defaults read $SDKROOT/SDKSettings buildSettings]
-        }] {
+        }]} {
             catch {
                 set info [exec defaults read $SDKROOT/SDKSettings DefaultProperties \
 			      -dict MACOSX_DEPLOYMENT_TARGET]
@@ -126,6 +142,7 @@ if {[string match macosx-* $platform]} {
         regsub -all {[\n"\;=\{\}]+} $info "" info ;#" help emacs hilighting
         regsub -all {\s+} $info " " info
         set osxmin [lindex $info 1]
+        }
     } else {
         # use the current platform
         foreach {v1 v2 v3} [split $::tcl_platform(osVersion) .] break
@@ -143,8 +160,10 @@ if {[string match macosx-* $platform]} {
         # set info [exec lipo -info /usr/lib/libSystem.dylib]
         # set plats [split [string trim [lindex [split $info :] 2]]]
     }
-    if {[info exists ::env(osxmin)] && $::env(osxmin) ne ""} {
-        set osxmin $::env(osxmin)
+    }
+    }
+    if {$SDKROOT eq ""} {
+        set SDKROOT /
     }
     set universal 0
     catch {