[Fix] Replace PWD with getcwd

PWD is not always the same as current working directory.

This is a problem when calling tests from ctest: the working directory
is changed, but the value of env::PWD is then incorrect.
Kernel files are then not found.

Using this system call the directory is correctly returned.

include/occa/io/utils.hpp

@@ -22,6 +22,8 @@ namespace occa {
     const std::string& cachePath();
     const std::string& libraryPath();
 
+    std::string currentWorkingDirectory();
+
     void endWithSlash(std::string &dir);
     std::string endWithSlash(const std::string &dir);
 

src/io/utils.cpp

@@ -65,6 +65,16 @@ namespace occa {
       return path;
     }
 
+    std::string currentWorkingDirectory() {
+      char cwdBuff[FILENAME_MAX];
+#if (OCCA_OS == OCCA_WINDOWS_OS)
+      _getcwd(cwdBuff, sizeof(cwdBuff));
+#else
+      getcwd(cwdBuff, sizeof(cwdBuff));
+#endif
+      return endWithSlash(std::string(cwdBuff));
+    }
+
     void endWithSlash(std::string &dir) {
       const int chars = (int) dir.size();
       if ((0 < chars) &&
@@ -167,7 +177,7 @@ namespace occa {
       expFilename = fo.expand(expFilename);
 
       if (makeAbsolute && !isAbsolutePath(expFilename)) {
-        expFilename = env::PWD + expFilename;
+        expFilename = currentWorkingDirectory() + expFilename;
       }
       return expFilename;
     }

tests/src/io/utils.cpp

@@ -87,7 +87,7 @@ void testPathMethods() {
             "b");
 
   ASSERT_EQ(occa::io::dirname("b.okl"),
-            occa::env::PWD);
+            occa::io::currentWorkingDirectory());
   ASSERT_EQ(occa::io::dirname("/a/b.okl"),
             "/a/");
   ASSERT_EQ(occa::io::dirname("/a"),