Set up test framework with demo test

lib/CMakeLists.txt

@@ -1,5 +1,6 @@
 add_library(gemhadar_lib
     "fd_io.c"
+    "url.c"
 )
 target_include_directories(gemhadar_lib PUBLIC "include")
 set_property(TARGET gemhadar_lib PROPERTY C_STANDARD 11)

lib/include/url.h

@@ -0,0 +1,6 @@
+#ifndef URL_H
+#define URL_H
+
+int foo(void);
+
+#endif

lib/url.c

@@ -0,0 +1,6 @@
+#include "url.h"
+
+int foo(void)
+{
+    return 42;
+}