glsl/tests/warnings-test: error if zero tests were executed
glsl/tests/warnings-test: error if zero tests were executed

We don't want to lie ourselves that 'everything is fine' when no tests
were found/ran.

Signed-off-by: Emil Velikov <f20878473f414da183da19ee25c8722cc1d711e4@collabora.com>
Acked-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>
Reviewed-by: Eric Engestrom <de0b63cf2dfb1fae8ed3c3b4244856a05677d4f0@imgtec.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler