update m_featureRoots less aggressively

it's not necessary to immediately re-calculate the roots after assigning
QMAKE_PLATFORM - it's sufficient to do it on-demand, so merely
invalidate them. this avoids that we re-calculate them multiple times
without ever using them in between while processing specs with
distributed platform assignments.

Change-Id: If508594764811b96a577fc81c5ded34ab0453148
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>
(cherry picked from qtcreator/28df27d924bb407791a76de8159c9ffa6efde283)
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

diff --git a/src/linguist/shared/qmakeevaluator.cpp b/src/linguist/shared/qmakeevaluator.cpp
index 281385a..907666d 100644 (file)
--- a/src/linguist/shared/qmakeevaluator.cpp
+++ b/src/linguist/shared/qmakeevaluator.cpp
@@ -939,7 +939,7 @@ void QMakeEvaluator::visitProVariable(
     if (varName == statics.strTEMPLATE)
         setTemplate();
     else if (varName == statics.strQMAKE_PLATFORM)
-        updateFeaturePaths();
+        m_featureRoots = 0;
 #ifdef PROEVALUATOR_FULL
     else if (varName == statics.strREQUIRES)
         checkRequirements(values(varName));
@@ -1163,6 +1163,7 @@ bool QMakeEvaluator::loadSpecInternal()
 #endif
     valuesRef(ProKey("QMAKESPEC")) << ProString(m_qmakespec);
     m_qmakespecName = IoUtils::fileName(m_qmakespec).toString();
+    // This also ensures that m_featureRoots is valid.
     if (evaluateFeatureFile(QLatin1String("spec_post.prf")) != ReturnTrue)
         return false;
     // The MinGW and x-build specs may change the separator; $$shell_{path,quote}() need it