stub loader_platform_executable_path()

Index: loader/vk_loader_platform.h
--- loader/vk_loader_platform.h.orig
+++ loader/vk_loader_platform.h
@@ -42,7 +42,7 @@
 #include "dlopen_fuchsia.h"
 #endif  // defined(__Fuchsia__)
 
-#if defined(__linux__) || defined(__APPLE__) || defined(__Fuchsia__) || defined(__QNXNTO__) || defined(__FreeBSD__)
+#if defined(__unix__) || defined(__APPLE__) || defined(__Fuchsia__) || defined(__QNXNTO__) || defined(__FreeBSD__)
 #include <unistd.h>
 // Note: The following file is for dynamic loading:
 #include <dlfcn.h>
@@ -50,7 +50,7 @@
 #include <stdlib.h>
 #include <libgen.h>
 
-#elif defined(_WIN32)  // defined(__linux__)
+#elif defined(_WIN32)  // defined(__unix__)
 /* Windows-specific common code: */
 // WinBase.h defines CreateSemaphore and synchapi.h defines CreateEvent
 //  undefine them to avoid conflicts with VkLayerDispatchTable struct members.
@@ -102,7 +102,7 @@
 // Override layer information
 #define VK_OVERRIDE_LAYER_NAME "VK_LAYER_LUNARG_override"
 
-#if defined(__linux__) || defined(__APPLE__) || defined(__Fuchsia__) || defined(__QNXNTO__) || defined(__FreeBSD__)
+#if defined(__unix__) || defined(__APPLE__) || defined(__Fuchsia__) || defined(__QNXNTO__) || defined(__FreeBSD__)
 /* Linux-specific common code: */
 
 // VK Library Filenames, Paths, etc.:
@@ -156,7 +156,7 @@ static inline bool loader_platform_is_path_absolute(co
 
 static inline char *loader_platform_dirname(char *path) { return dirname(path); }
 
-#if defined(__linux__)
+#if defined(__unix__)
 
 // find application path + name. Path cannot be longer than 1024, returns NULL if it is greater than that.
 static inline char *loader_platform_executable_path(char *buffer, size_t size) {
@@ -166,7 +166,11 @@ static inline char *loader_platform_executable_path(ch
     buffer[count] = '\0';
     return buffer;
 }
-#elif defined(__APPLE__) // defined(__linux__)
+#elif defined(__OpenBSD__) // defined(__APPLE__)
+static inline char *loader_platform_executable_path(char *buffer, size_t size) {
+    return NULL;
+}
+#elif defined(__APPLE__) // defined(__unix__)
 #include <libproc.h>
 static inline char *loader_platform_executable_path(char *buffer, size_t size) {
     pid_t pid = getpid();
@@ -293,7 +297,7 @@ static inline void loader_platform_thread_cond_wait(lo
 }
 static inline void loader_platform_thread_cond_broadcast(loader_platform_thread_cond *pCond) { pthread_cond_broadcast(pCond); }
 
-#elif defined(_WIN32)  // defined(__linux__)
+#elif defined(_WIN32)  // defined(__unix__)
 
 // VK Library Filenames, Paths, etc.:
 #define PATH_SEPARATOR ';'
