qmake-1.0 PG: sync debug variant generation with qmake5-1.0 PG.

Adds a new option qt4.debug_variant - defaulting to yes, but the
PG-generated debug variant can be disabled by setting it to no.

Note that the variant checking code can stay in pre-extract, since it's
only checking information available in the database, not any actual file
location. Otherwise, it would have needed to be moved from pre-extract
to pre-configure in order to work correctly in trace mode, or if we ever
decide to implement something like background pre-fetching and
-extraction of ports.

See: https://trac.macports.org/ticket/58229

_resources/port1.0/group/qmake-1.0.tcl

@@ -6,6 +6,10 @@
 # PortGroup                     qmake 1.0
 
 PortGroup                       qt4 1.0
+PortGroup                       active_variants 1.1
+
+options qt4.debug_variant
+default qt4.debug_variant yes
 
 pre-configure {
     configure.cmd                   ${qt_qmake_cmd}
@@ -28,8 +32,17 @@ pre-configure {
     }
 }
 
-variant debug description "Enable debug binaries" {
-    configure.pre_args-append   "CONFIG+=debug"
+# add debug variant if one does not exist and one is requested via qt4.debug_variant
+# variant is added in eval_variants so that qt4.debug_variant can be set anywhere in the Portfile
+rename ::eval_variants ::real_qmake_eval_variants
+proc eval_variants {variations} {
+    global qt4.debug_variant
+    if { ![variant_exists debug] && [tbool qt4.debug_variant] } {
+        variant debug description {Build both release and debug binaries and libraries} {
+            configure.pre_args-append   "CONFIG+=debug"
+        }
+    }
+    uplevel ::real_qmake_eval_variants $variations
 }
 
 # check for +debug variant of this port, and make sure Qt was
@@ -39,10 +52,22 @@ platform darwin {
         if {[variant_exists debug] && \
             [variant_isset debug] && \
            ![info exists building_qt4]} {
-            if {![file exists ${qt_frameworks_dir}/QtCore.framework/QtCore_debug]} {
+            if {![catch {set result [active_variants "qt4-mac" "debug" ""]}]} {
+                if {$result} {
+                    # code to be executed if $depspec is active with at least all variants in
+                    # $required and none from $forbidden
+                } else {
+                    # code to be executed if $depspec is active, but either not with all
+                    # variants in $required or any variant in $forbidden
+                    return -code error "\n\nERROR:\n\
+In order to install this port with variant +debug,\
+qt4-mac must also be installed with variant +debug.\n"
+                }
+            } else {
+                # code to be executed if $depspec isn't active
                 return -code error "\n\nERROR:\n\
-In order to install this port as +debug,
-Qt4 must also be installed with +debug.\n"
+Requested to install this port with variant +debug,\
+but qt4-mac is not installed or installed but not active.\n"
             }
         }
     }