Fix the test "TestFileLister" by giving precisely the source directory instead of guessing it.
Author: Florent Pruvost <florent.pruvost@inria.fr>

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 467e6e95e..d68d83e3d 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -85,6 +85,7 @@ if (BUILD_TESTS)
             elseif(TEST ${NAME})
             else()
                 add_test(NAME ${NAME} COMMAND $<TARGET_FILE:testrunner> ${NAME} WORKING_DIRECTORY ${CMAKE_RUNTIME_OUTPUT_DIRECTORY})
+                set_tests_properties(${NAME} PROPERTIES ENVIRONMENT "PROJECT_SOURCE_DIR=${PROJECT_SOURCE_DIR}")
             endif()
         endfunction()
 
diff --git a/test/testfilelister.cpp b/test/testfilelister.cpp
index 3e2f56dfc..ecf0f9c6e 100644
--- a/test/testfilelister.cpp
+++ b/test/testfilelister.cpp
@@ -45,15 +45,7 @@ private:
 
     // TODO: generate file list instead
     static std::string findBaseDir() {
-        std::string basedir;
-        while (!Path::isDirectory(Path::join(basedir, ".github"))) {
-            const std::string abspath = Path::getAbsoluteFilePath(basedir);
-            basedir += "../";
-            // no more going up
-            if (Path::getAbsoluteFilePath(basedir) == abspath)
-                throw std::runtime_error("could not find repository root directory");
-        }
-        return basedir;
+        return Path::getAbsoluteFilePath(std::getenv("PROJECT_SOURCE_DIR")) + "/";
     }
 
     void recursiveAddFiles() const {