raylib: disable build on ubuntu focal (#34150)

build

system/ui/SConscript

@@ -1,7 +1,12 @@
+import subprocess
+
 Import('env', 'arch', 'common')
 
 renv = env.Clone()
 
+UBUNTU_FOCAL = int(subprocess.check_output('[ -f /etc/os-release ] && . /etc/os-release && [ "$ID" = "ubuntu" ] && [ "$VERSION_ID" = "20.04" ] && echo 1 || echo 0', shell=True, encoding='utf-8').rstrip())
+
+if not UBUNTU_FOCAL:
   rayutil = env.Library("rayutil", ['raylib/util.cc'], LIBS='raylib')
   linked_libs = ['raylib', rayutil, common]
   renv['LIBPATH'] += [f'#third_party/raylib/{arch}/']