Add git-based build information for better issue tracking (#1232)

* Add git-based build information for better issue tracking

* macOS fix

* "build (hash)" and "CMAKE_SOURCE_DIR" changes

* Redo "CMAKE_CURRENT_SOURCE_DIR" and clearer build messages

* Fix conditional dependency on missing target

* Broke out build-info.cmake, added find_package fallback, and added build into to all examples, added dependencies to Makefile

* 4 space indenting for cmake, attempt to clean up my mess in Makefile

* Short hash, less fancy Makefile, and don't modify build-info.h if it wouldn't change it

examples/quantize-stats/quantize-stats.cpp

@@ -1,4 +1,5 @@
 #include "ggml.h"
+#include "build-info.h"
 
 #define LLAMA_API_INTERNAL
 #include "llama.h"
@@ -308,6 +309,8 @@ int main(int argc, char ** argv) {
         return 1;
     }
 
+    fprintf(stderr, "%s: build = %d (%s)\n", __func__, BUILD_NUMBER, BUILD_COMMIT);
+
     // load the model
     fprintf(stderr, "Loading model\n");