check for symbols defined in the library

Author: yeesian

deps/build.jl

@@ -1,7 +1,9 @@
 using BinDeps, Compat
 @BinDeps.setup
 
-libgeos = library_dependency("libgeos",aliases=["libgeos_c", "libgeos_c-1"])
+libgeos = library_dependency("libgeos",aliases=["libgeos_c", "libgeos_c-1"], validate = function(path, handle)
+    return @compat(Libdl.dlsym_e(handle,:initGEOS)) != C_NULL
+end)
 
 version = "3.4.2"