configure: support discarding selected test results with -recheck

especially during debugging, it is often necessary to re-run only one
(or a few) tests, where -recheck-all would be wasteful.

Task-number: QTBUG-64059
Change-Id: I9410894dec4289ff832d7f75e04f9b60fe76c57c
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

config_help.txt

@@ -66,8 +66,10 @@ Configure meta:
   -redo ................ Re-configure with previously used options.
                          Additional options may be passed, but will not be
                          saved for later use by -redo.
-  -recheck ............. Discard cached negative configure test results.
+  -recheck [test,...] .. Discard cached negative configure test results.
                          Use this after installing missing dependencies.
+                         Alternatively, if tests are specified, only their
+                         results are discarded.
   -recheck-all ......... Discard all cached configure test results.
 
   -feature-<feature> ... Enable <feature>

mkspecs/features/data/configure.json

@@ -9,7 +9,7 @@
 
             "continue": "void",
 
-            "recheck": { "type": "void", "name": "cache_use", "value": "positive" },
+            "recheck": { "type": "optionalString", "name": "cache_recheck" },
             "recheck-all": { "type": "void", "name": "cache_use", "value": "none" },
 
             "redo": { "type": "redo" },

mkspecs/features/qt_configure.prf

@@ -2041,14 +2041,28 @@ qtConfCheckErrors()
 
 QMAKE_CONFIG_CACHE = $$OUT_PWD/config.cache
 QMAKE_CONFIG_CACHE_USE = $$eval(config.input.cache_use)
+cache_recheck = $$eval(config.input.cache_recheck)
+equals(cache_recheck, yes) {
+    QMAKE_CONFIG_CACHE_USE = positive
+    cache_recheck =
+}
 isEmpty(QMAKE_CONFIG_CACHE_USE): \
     QMAKE_CONFIG_CACHE_USE = all
 !equals(QMAKE_CONFIG_CACHE_USE, none) {
     include($$QMAKE_CONFIG_CACHE, , true)
     # this crudely determines when to discard the cache. this also catches the case
     # of no cache being there in the first place.
-    !equals(cache.platform, $$[QMAKE_SPEC])|!equals(cache.xplatform, $$[QMAKE_XSPEC]): \
+    !equals(cache.platform, $$[QMAKE_SPEC])|!equals(cache.xplatform, $$[QMAKE_XSPEC]) {
         QMAKE_CONFIG_CACHE_USE = none
+    } else: !isEmpty(cache_recheck) {
+        for (cr, $$list($$split(cache_recheck, ","))) {
+            !isEmpty(cache.$${cr}._KEYS_) {
+                cache.$${cr}._KEYS_ =
+            } else {
+                qtConfAddWarning("Attempting to discard non-cached result '$$cr'.")
+            }
+        }
+    }
 }
 equals(QMAKE_CONFIG_CACHE_USE, none) {
     cont = \