cmakeprojectmanager: save files before build

This code path (CMakeBuildSystem::buildCMakeTarget) is taken
when building a specific target, such as when activating
Build > Build for Run Configuration. Building via e.g. Ctrl+B
takes a different code path, so this shouldn't be called more
than necessary.

Fixes: QTCREATORBUG-25276
Change-Id: I362bafda43460eaeac9cbf0f053bf457a76702f1
Reviewed-by: Cristian Adam <cristian.adam@qt.io>

src/plugins/cmakeprojectmanager/cmakebuildsystem.cpp

@@ -43,6 +43,7 @@
 #include <cpptools/cpptoolsconstants.h>
 #include <cpptools/generatedcodemodelsupport.h>
 #include <projectexplorer/kitinformation.h>
+#include <projectexplorer/projectexplorer.h>
 #include <projectexplorer/projectexplorerconstants.h>
 #include <projectexplorer/session.h>
 #include <projectexplorer/target.h>
@@ -454,6 +455,7 @@ void CMakeBuildSystem::runCMakeWithExtraArguments()
 void CMakeBuildSystem::buildCMakeTarget(const QString &buildTarget)
 {
     QTC_ASSERT(!buildTarget.isEmpty(), return);
+    if (ProjectExplorerPlugin::saveModifiedFiles())
         cmakeBuildConfiguration()->buildTarget(buildTarget);
 }