gnatcheck: fix how generic inst walking diagnostics are emitted

Fix also testcase to make it Windows-compatible

Author: thvnx

lkql_jit/language/src/main/java/com/adacore/lkql_jit/checker/built_ins/NodeCheckerFunction.java

@@ -110,8 +110,7 @@ public Object alwaysTrue(VirtualFrame frame, Libadalang.AdaNode root) {
                                     CheckerUtils.MessageKind.ERROR,
                                     e.getMessage(),
                                     new LalLocationWrapper(currentNode, context.linesCache),
-                                    new SourceSectionWrapper(this.callNode.getSourceSection()),
-                                    rootUnit.getFileName(true));
+                                    new SourceSectionWrapper(this.callNode.getSourceSection()));
                     continue;
                 }
 

testsuite/tests/gnatcheck_errors/generic_inst_walking/test.out

@@ -32,6 +32,6 @@ Total gnatcheck failures: 1
 
 6. Gnatcheck internal errors
 
-test.adb:2:04: error: internal issue at checker.lkql:4:22: test.adb:2:4-2:28: dereferencing a null access [/test.adb]
+/test.adb:2:04: error: internal issue at checker.lkql:4:22: test.adb:2:4-2:28: dereferencing a null access
 
 >>>program returned status code 2

testsuite/tests/gnatcheck_errors/generic_inst_walking/test.yaml

@@ -1,4 +1,6 @@
 driver: gnatcheck
 project: prj.gpr
+extra_args: ['-l']
 rules:
   - +Rderiving_from_predefined_type
+canonicalize_backslashes: True