Debugger: Have a generic "GDB in PATH on Build Device" item

This is only checked at run-time, but allows smoother creation of
kits for standard setups as the (possibly remote) full path is
not needed.

Remove the DebuggerKitAspect::fixup() implementation. Too much magic
by now, and worst thing that could happen is a non-matching debugger
that will clearly bark when used.

Change-Id: If2414610d479a5b93c3e6227b8736ddc61f70635
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/remotelinux/linuxdevice.cpp

@@ -339,7 +339,7 @@ Environment LinuxDevicePrivate::getEnvironment()
         return m_environmentCache.value();
 
     QtcProcess getEnvProc;
-    getEnvProc.setCommand({FilePath("env").onDevice(q->rootPath()), {}});
+    getEnvProc.setCommand({q->filePath("env"), {}});
     getEnvProc.runBlocking();
 
     const QString remoteOutput = getEnvProc.cleanedStdOut();