Re-enabling narrowing errors (#1144)

Fixes narrowing conversion build errors in test_common

Removing disable of narrowing errors in main CMakeLists.txt
and moving it down to specific test_conformance suite's 
CMakeLists.txt where there are many more build errors revealed
from this fix. 

Fixes a few simple issues under test_conformance in the process.

Contributes #787

Signed-off-by: Ellen Norris-Thompson <ellen.norris-thompson@arm.com>

---------

Signed-off-by: Ellen Norris-Thompson <ellen.norris-thompson@arm.com>

test_conformance/spir/main.cpp

@@ -155,7 +155,8 @@ static void get_spir_version(cl_device_id device,
     {
         auto major = v[v.find('.') - 1];
         auto minor = v[v.find('.') + 1];
-        versions.push_back(Version{ major - '0', minor - '0' });
+        versions.push_back(
+            Version{ (cl_uint)(major - '0'), (cl_uint)(minor - '0') });
     }
 }