Utils: Replace Environment::isSameExecutable()

... by FilePath::isSameExecutable().

The only non-mechanical case is the use inside QmakeBuildSystem::testToolChain
using a build environment instead of the FilePath's device environment.

This make a difference in theory due to the use of PATHEXT in the actual
check, but I believe the case that someone creates a 'qmake.foo' and
a 'qmake.bar', adds .foo and .bar to PATHEXT and then complains that
there's a warning missing about not-matching mkspecs has zero
likelihood in reality (and will break other places in Creator anyway).

Change-Id: Id6a8d1e4dc2eb74ca81610ccb1c4ee94c6f47e12
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/plugins/qtsupport/qtversionmanager.cpp

@@ -421,8 +421,7 @@ static void findSystemQt()
         if (BuildableHelperLibrary::isQtChooser(qmakePath))
             continue;
         const auto isSameQmake = [qmakePath](const QtVersion *version) {
-            return Environment::systemEnvironment().
-                    isSameExecutable(qmakePath.toString(), version->qmakeFilePath().toString());
+            return qmakePath.isSameExecutable(version->qmakeFilePath());
         };
         if (contains(m_versions, isSameQmake))
             continue;