Only allow to build on linux, macos or windows (limited by juce)

Signed-off-by: falkTX <falktx@falktx.com>

meson.build

@@ -41,8 +41,10 @@ if host_machine.system() == 'darwin'
     os_darwin = true
 elif host_machine.system() == 'windows'
     os_windows = true
-else
+elif host_machine.system() == 'linux'
     os_linux = true
+else
+    error('unsupported system')
 endif
 
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