[CALCITE-6385] LintTest fails when run in source distribution

The testContributorsFileIsSorted and testMailmapFile tests fail cause
they rely on git and there is no git info available in source
distribution.

In fact the tests don't really need git and the paths to the .mailmap
and contributor.yml files can be specified explicitly. This removes
the git requirement and also makes the tests more efficient since there
is no process calls and lookup involved.

build.gradle.kts

@@ -826,6 +826,7 @@ allprojects {
                 passProperty("user.country", "tr")
                 passProperty("user.timezone", "UTC")
                 passProperty("calcite.avatica.version", props.string("calcite.avatica.version"))
+                passProperty("gradle.rootDir", rootDir.toString())
                 val props = System.getProperties()
                 for (e in props.propertyNames() as `java.util`.Enumeration<String>) {
                     if (e.startsWith("calcite.") || e.startsWith("avatica.")) {

core/src/test/java/org/apache/calcite/test/LintTest.java

@@ -37,6 +37,8 @@
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.io.StringWriter;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.List;
@@ -46,10 +48,6 @@
 import java.util.regex.Pattern;
 import java.util.stream.Stream;
 
-import static com.google.common.collect.Iterables.getOnlyElement;
-
-import static org.apache.calcite.util.Util.filter;
-
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.empty;
@@ -64,6 +62,7 @@ class LintTest {
    * space. */
   private static final Pattern CALCITE_PATTERN =
       Pattern.compile("^(\\[CALCITE-[0-9]{1,4}][ ]).*");
+  private static final Path ROOT_PATH = Paths.get(System.getProperty("gradle.rootDir"));
 
   @SuppressWarnings("Convert2MethodRef") // JDK 8 requires lambdas
   private Puffin.Program<GlobalState> makeProgram() {
@@ -397,10 +396,7 @@ private static void checkMessage(String subject, String body,
   /** Ensures that the {@code contributors.yml} file is sorted by name. */
   @Test void testContributorsFileIsSorted() throws IOException {
     final ObjectMapper mapper = new YAMLMapper();
-    final List<File> files = TestUnsafe.getTextFiles();
-    final File contributorsFile =
-        getOnlyElement(
-            filter(files, f -> f.getName().equals("contributors.yml")));
+    final File contributorsFile = ROOT_PATH.resolve("site/_data/contributors.yml").toFile();
     JavaType listType =
         mapper.getTypeFactory()
             .constructCollectionType(List.class, Contributor.class);
@@ -416,12 +412,9 @@ private static void checkMessage(String subject, String body,
 
   /** Ensures that the {@code .mailmap} file is sorted. */
   @Test void testMailmapFile() {
-    final List<File> files = TestUnsafe.getTextFiles();
-    final File contributorsFile =
-        getOnlyElement(
-            filter(files, f -> f.getName().equals(".mailmap")));
+    final File mailmapFile = ROOT_PATH.resolve(".mailmap").toFile();
     final List<String> lines = new ArrayList<>();
-    forEachLineIn(contributorsFile, line -> {
+    forEachLineIn(mailmapFile, line -> {
       if (!line.startsWith("#")) {
         lines.add(line);
       }