add epoxy_set_library_path for android

this is used in termux to load angle a mobile driver optimised for mali

currently the regular epoxy packet lacks this function adding to the
already overwhelming confusion over what actually works. everything
works in termux but there are many paths that fail. I am trying to widen
the road that lead to life

the angle drivers have been hard coded for simplicity. Never calling
this function will use the regular driver

Author: john-peterson

include/epoxy/common.h

@@ -57,6 +57,9 @@ EPOXY_BEGIN_DECLS
 
 EPOXY_PUBLIC bool epoxy_extension_in_string(const char *extension_list,
                                             const char *ext);
+#if defined(__ANDROID__)
+EPOXY_PUBLIC void epoxy_set_library_path(const char * path);
+#endif
 
 EPOXY_END_DECLS
 

src/dispatch_common.c

@@ -179,10 +179,16 @@
 #define GLES1_LIB "libGLESv1_CM.so"
 #define GLES2_LIB "libGLESv2.so"
 #elif defined(__ANDROID__)
-#define GLX_LIB "libGLESv2.so"
-#define EGL_LIB "libEGL.so"
-#define GLES1_LIB "libGLESv1_CM.so"
-#define GLES2_LIB "libGLESv2.so"
+#define GLX_LIB GLES2_LIB
+static char EGL_LIB[256] = "libEGL.so";
+static char GLES1_LIB[256] = "libGLESv1_CM.so";
+static char GLES2_LIB[256] = "libGLESv2.so";
+EPOXY_PUBLIC void epoxy_set_library_path(const char * path) {
+    char *prefix = getenv("PREFIX");
+    snprintf(EGL_LIB, sizeof(EGL_LIB), "%s/%s/libEGL_angle.so", prefix, path);
+    snprintf(GLES1_LIB, sizeof(GLES1_LIB), "%s/%s/libGLESv1_CM_angle.so", prefix, path);
+    snprintf(GLES2_LIB, sizeof(GLES2_LIB), "%s/%s/libGLESv2_angle.so", prefix, path);
+}
 #elif defined(_WIN32)
 #define EGL_LIB "libEGL.dll"
 #define GLES1_LIB "libGLES_CM.dll"