[build] switch to CMake

This is very much a work in progress.

test/src/main.cpp

@@ -1,5 +1,20 @@
 #include <mbgl/test.hpp>
+#include <unistd.h>
+#include <cstring>
+#include <cerrno>
+#include <cstdio>
+
+#define xstr(s) str(s)
+#define str(s) #s
 
 int main(int argc, char *argv[]) {
+#ifdef WORK_DIRECTORY
+    const int result = chdir(xstr(WORK_DIRECTORY));
+    if (result != 0) {
+        fprintf(stderr, "failed to change directory: %s\n", strerror(errno));
+        return errno;
+    }
+#endif
+
     return mbgl::runTests(argc, argv);
 }