Remove QTC_ASSERT because unset toolchain is a valid condition

Change-Id: I2ba710cf4e0af31138787bb7859302ad3a3f3d03
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Cristian Adam <cristian.adam@qt.io>

src/plugins/cmakeprojectmanager/cmakebuildconfiguration.cpp

@@ -808,7 +808,8 @@ static bool isDocker(const Kit *k)
 static bool isWindowsARM64(const Kit *k)
 {
     ToolChain *toolchain = ToolChainKitAspect::cxxToolChain(k);
-    QTC_ASSERT(toolchain, return false);
+    if (!toolchain)
+        return false;
     const Abi targetAbi = toolchain->targetAbi();
     return targetAbi.os() == Abi::WindowsOS && targetAbi.architecture() == Abi::ArmArchitecture
             && targetAbi.wordWidth() == 64;