SquishTests: Fix default settings test

Depending on the presence of the llvm that had been used when building
QC we need to expect its clang.
Use special environment variable to be able to do this correctly.

Change-Id: I2497bbd96483f37aa90842d7fffa5d0a8103ff45
Reviewed-by: Robert Löhning <robert.loehning@qt.io>

tests/system/suite_general/tst_default_settings/test.py

@@ -31,6 +31,13 @@ def __checkKits__():
     mouseClick(waitForObjectItem(":Options_QListView", "Kits"))
     # check compilers
     expectedCompilers = __getExpectedCompilers__()
+    llvmForBuild = os.getenv("SYSTEST_LLVM_FROM_BUILD", None)
+    if llvmForBuild is not None:
+        internalClangExe = os.path.join(llvmForBuild, "bin", "clang")
+        if platform.system() in ("Microsoft", "Windows"):
+            internalClangExe.append(".exe")
+        if os.path.exists(internalClangExe):
+            expectedCompilers.append(internalClangExe)
     foundCompilers = []
     foundCompilerNames = []
     clickOnTab(":Options.qt_tabwidget_tabbar_QTabBar", "Compilers")