Cherry-pick warning about developer_dir pointing to non-existing path

This conflicted, because https://trac.macports.org/changeset/89996 isn't in release2-0 yet.

git-svn-id: https://svn.macports.org/repository/macports/branches/release_2_0/base@90805 d073be05-634f-4543-b044-5fe20cf6d1d6

ChangeLog

@@ -27,6 +27,9 @@ Unreleased changes:
       r90018-r90019,r90024,r90031)
 
 Release 2.0.5 (unreleased)
+    - warn about non-existing developer_dir when it's set in macports.conf
+      (cal in 90802)
+
     - port automatically installs bsdmake when there's no bsdmake in $PATH and a
       port sets build.type bsd (#33355, cal in r90650)
 

src/macports1.0/macports.tcl

@@ -898,6 +898,14 @@ proc mportinit {{up_ui_options {}} {up_options {}} {up_variations {}}} {
         trace add variable macports::xcodebuildcmd read macports::setxcodeinfo
     }
 
+    if {[info exists developer_dir]} {
+        if {$os_platform == "darwin" && ![file isdirectory $developer_dir]} {
+            ui_warn "Your developer_dir setting in macports.conf points to a non-existing directory.\
+                Since this is known to cause problems, please correct the setting or comment it and let\
+                macports auto-discover the correct path."
+        }
+    }
+
     if {[getuid] == 0 && $os_major >= 11 && $os_platform == "darwin" && [vercmp $xcodeversion 4.3] >= 0} {
         macports::copy_xcode_plist $env(HOME)
     }