Make LUA scripting work even if proxmark3 is called from arbitrary working directory

- add @gpakosz whereami library (https://github.com/gpakosz/whereami) in order to ...
- determine and set absolute paths for LUA scripts and LUA libraries

client/whereami.h

@@ -0,0 +1,65 @@
+// (‑●‑●)> released under the WTFPL v2 license, by Gregory Pakosz (@gpakosz)
+// https://github.com/gpakosz/whereami
+
+#ifndef WHEREAMI_H
+#define WHEREAMI_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef WAI_FUNCSPEC
+  #define WAI_FUNCSPEC
+#endif
+#ifndef WAI_PREFIX
+#define WAI_PREFIX(function) wai_##function
+#endif
+
+/**
+ * Returns the path to the current executable.
+ *
+ * Usage:
+ *  - first call `int length = wai_getExecutablePath(NULL, 0, NULL);` to
+ *    retrieve the length of the path
+ *  - allocate the destination buffer with `path = (char*)malloc(length + 1);`
+ *  - call `wai_getExecutablePath(path, length, NULL)` again to retrieve the
+ *    path
+ *  - add a terminal NUL character with `path[length] = '\0';`
+ *
+ * @param out destination buffer, optional
+ * @param capacity destination buffer capacity
+ * @param dirname_length optional recipient for the length of the dirname part
+ *   of the path.
+ *
+ * @return the length of the executable path on success (without a terminal NUL
+ * character), otherwise `-1`
+ */
+WAI_FUNCSPEC
+int WAI_PREFIX(getExecutablePath)(char* out, int capacity, int* dirname_length);
+
+/**
+ * Returns the path to the current module
+ *
+ * Usage:
+ *  - first call `int length = wai_getModulePath(NULL, 0, NULL);` to retrieve
+ *    the length  of the path
+ *  - allocate the destination buffer with `path = (char*)malloc(length + 1);`
+ *  - call `wai_getModulePath(path, length, NULL)` again to retrieve the path
+ *  - add a terminal NUL character with `path[length] = '\0';`
+ *
+ * @param out destination buffer, optional
+ * @param capacity destination buffer capacity
+ * @param dirname_length optional recipient for the length of the dirname part
+ *   of the path.
+ *
+ * @return the length of the module path on success (without a terminal NUL
+ * character), otherwise `-1`
+ */
+WAI_FUNCSPEC
+int WAI_PREFIX(getModulePath)(char* out, int capacity, int* dirname_length);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // #ifndef WHEREAMI_H