try to fix CI build failure:

```
Post Link Common
/bin/sh: 1: /home/runner/work/qgroundcontrol/qgroundcontrol/deploy/linux-fixup-rpaths.bash: not found
make: *** [staging/QGroundControl] Error 127
Makefile:2944: recipe for target 'staging/QGroundControl' failed
Error: Process completed with exit code 2.
```

QGCPostLinkCommon.pri

@@ -172,8 +172,8 @@ LinuxBuild {
         include($$PWD/custom/custom_deploy.pri)
     }
 
-    QMAKE_POST_LINK += && SEARCHDIR="$$DESTDIR/Qt" RPATHDIR="$$DESTDIR/Qt/libs" "$$SOURCE_DIR/deploy/linux-fixup-rpaths.bash"
+    QMAKE_POST_LINK += && SEARCHDIR="$$DESTDIR/Qt" RPATHDIR="$$DESTDIR/Qt/libs" "$$PWD/deploy/linux-fixup-rpaths.bash"
 
     # https://doc.qt.io/qt-5/qt-conf.html
-    QMAKE_POST_LINK += && cp "$$SOURCE_DIR/deploy/qt.conf" "$$DESTDIR"
+    QMAKE_POST_LINK += && $$QMAKE_COPY "$$SOURCE_DIR/deploy/qt.conf" "$$DESTDIR"
 }

deploy/linux-fixup-rpaths.bash

@@ -1,4 +1,4 @@
-#!/usr/bin/bash
+#!/usr/bin/env bash
 #
 # Premise:
 # Shared libraries (Qt, airmap, etc) on Linux are built without knowing where