Comment 1 for bug 1921549

Contents of my build directory:

 ls -l
drwxr-xr-x - jan jan 26 Mar 20:34 -- bin
.rw-r--r-- 6.4k jan jan 26 Mar 20:34 -- cmake_install.cmake
.rw-r--r-- 146k jan jan 26 Mar 20:34 -- CMakeCache.txt
drwxr-xr-x - jan jan 26 Mar 20:35 -- CMakeFiles
.rw-r--r-- 6.3k jan jan 26 Mar 20:34 -- CPackConfig.cmake
.rw-r--r-- 6.6k jan jan 26 Mar 20:34 -- CPackSourceConfig.cmake
.rw-r--r-- 326k jan jan 26 Mar 20:34 -- CTestTestfile.cmake
.rw-r--r-- 2.5k jan jan 26 Mar 20:34 -- DartConfiguration.tcl
drwxr-xr-x - jan jan 26 Mar 20:34 -- download
drwxr-xr-x - jan jan 26 Mar 20:35 -- lib
.rw-r--r-- 472k jan jan 26 Mar 20:34 -- libfidlib.a
.rw-r--r-- 10k jan jan 26 Mar 20:34 -- libFpClassify.a
.rw-r--r-- 326k jan jan 26 Mar 20:34 -- libKaitai.a
drwxr-xr-x - jan jan 26 Mar 20:34 -- libkeyfinder-prefix
.rw-r--r-- 109k jan jan 26 Mar 20:34 -- libmixxx-hidapi.a
.rw-r--r-- 667M jan jan 26 Mar 20:35 -- libmixxx-lib.a
.rw-r--r-- 40k jan jan 26 Mar 20:34 -- libmixxx-xwax.a
.rw-r--r-- 260k jan jan 26 Mar 20:34 -- libMP3GuessEnc.a
.rw-r--r-- 15k jan jan 26 Mar 20:34 -- libPortAudioRingBuffer.a
.rw-r--r-- 1.5M jan jan 26 Mar 20:34 -- libQtScriptByteArray.a
.rw-r--r-- 4.8M jan jan 26 Mar 20:34 -- libQueenMaryDsp.a
.rw-r--r-- 95k jan jan 26 Mar 20:34 -- libReplayGain.a
.rw-r--r-- 72k jan jan 26 Mar 20:34 -- libReverb.a
.rw-r--r-- 907k jan jan 26 Mar 20:34 -- Makefile
.rwxr-xr-x 361M jan jan 26 Mar 20:35 -- mixxx
drwxr-xr-x - jan jan 26 Mar 20:34 -- mixxx-lib_autogen
drwxr-xr-x - jan jan 26 Mar 20:34 -- mixxx-qrc_autogen
.rwxr-xr-x 395M jan jan 26 Mar 20:35 -- mixxx-test
drwxr-xr-x - jan jan 26 Mar 20:35 -- mixxx-test_autogen
drwxr-xr-x - jan jan 26 Mar 20:34 -- QtScriptByteArray_autogen
drwxr-xr-x - jan jan 26 Mar 20:34 -- src
drwxr-xr-x - jan jan 26 Mar 20:34 -- Testing

Looks like the res directory symlink is missing.