[Piglit] assertions reported as "pass"

[Brian Paul]

This seems wrong.  If I run the "arb_program_interface_query" tests (for 
example), the arb_program_interface_query-resource-query test hits an 
assertion:

state_tracker/st_glsl_to_tgsi.cpp:2394: virtual void 
glsl_to_tgsi_visitor::visit(ir_dereference_variable*): Assertion 
`var->data.location != -1' failed.

But piglit's recording that as a "pass" result for some reason.  Here's 
the whole json record:

"spec at arb_program_interface_query@arb_program_interface_query-resource-query": 
{
             "returncode": -6,
             "pid": 22913,
             "result": "pass",
             "subtests": {
                 "GL_UNIFORM_BLOCK(cs)": "skip",
                 "GL_PROGRAM_INPUT(fs)": "pass",
                 "__type__": "Subtests",
                 "GL_PROGRAM_INPUT(vs,fs)": "pass",
                 "GL_UNIFORM_BLOCK(tcs,tes)": "skip",
                 "GL_UNIFORM(cs)": "skip",
                 "GL_UNIFORM(vs,gs,fs)": "pass",
                 "GL_PROGRAM_INPUT(gs)": "pass",
                 "GL_PROGRAM_INPUT(vs)": "pass",
                 "GL_UNIFORM(tes,tcs)": "skip",
                 "GL_PROGRAM_INPUT(vs,gs)": "pass",
                 "GL_UNIFORM_BLOCK(vs,gs,fs)": "pass"
             },
             "out": "",
             "dmesg": "",
             "exception": null,
             "err": "arb_program_interface_query-resource-query: 
state_tracker/st_glsl_to_tgsi.cpp:2394: virtual void 
glsl_to_tgsi_visitor::visit(ir_dereference_variable*): Assertion 
`var->data.location != -1' failed.\n",
             "traceback": null,
             "__type__": "TestResult",
             "environment": 
"PIGLIT_SOURCE_DIR=\"/home2016/projects/piglit\" 
PIGLIT_PLATFORM=\"mixed_glx_egl\"",
             "command": 
"/home2016/projects/piglit/bin/arb_program_interface_query-resource-query -auto", 

             "time": {
                 "start": 1462821421.394709,
                 "end": 1462821421.446879,
                 "__type__": "TimeAttribute"
             }
         },

Can someone (Dylan?) look into that?  Thanks!

-Brian