1104 - '%s' ('%s') is not defined.

Description
A Function references a node which has not been defined.
Example
Config:
Test( 'RunTest' ) { .TestOutput = 'tmp/' .TestExecutable = 'test.exe' }
Output:
c:\Test\fbuild.bff(1):(1) FASTBuild Error #1104 - Test() - 'TestExecutable' ('test.exe') is not defined. Test( 'RunTest' ) ^ \--here
Fix:
Executable( 'Test' ) { .LinkerOutput = 'test.exe' } Test( 'RunTest' ) { .TestOutput = 'tmp/' .TestExecutable = 'test.exe' }