Fix recently-added testUsdAbcIndexedGeomArb

Invoke usdcat directly instead of going through the
test script which simply does the same thing. This
is similar to how the usdcat tests are set up and
avoids issues where usdcat may not be in the PATH
when the test is run.

See #1635

(Internal change: 2217289)

pxr/usd/plugin/usdAbc/CMakeLists.txt

@@ -70,7 +70,6 @@ pxr_test_scripts(
     testenv/testUsdAbcConversionSubdiv.py
     testenv/testUsdAbcFaceset.py
     testenv/testUsdAbcIndexedProperties.py
-    testenv/testUsdAbcIndexedGeomArb.py
     testenv/testUsdAbcInstancing.py
     testenv/testUsdAbcIsConstant.py
     testenv/testUsdAbcP_OldEncoding.py
@@ -115,8 +114,8 @@ pxr_install_test_dir(
 )
 
 pxr_install_test_dir(
-        SRC testenv/testUsdAbcIndexedGeomArb
-        DEST testUsdAbcIndexedGeomArb
+    SRC testenv/testUsdAbcIndexedGeomArb
+    DEST testUsdAbcIndexedGeomArb
 )
 
 pxr_install_test_dir(
@@ -213,7 +212,7 @@ pxr_register_test(testUsdAbcIndexedProperties
 
 pxr_register_test(testUsdAbcIndexedGeomArb
     PYTHON
-    COMMAND "${CMAKE_INSTALL_PREFIX}/tests/testUsdAbcIndexedGeomArb"
+    COMMAND "${CMAKE_INSTALL_PREFIX}/bin/usdcat hasColorSet.abc --out good_primvars_namespace_after_fix.usda"
     DIFF_COMPARE good_primvars_namespace_after_fix.usda
     EXPECTED_RETURN_CODE 0
     ENV