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/save-load-state/CMakeLists.txt

@@ -2,3 +2,6 @@ set(TARGET save-load-state)
 add_executable(${TARGET} save-load-state.cpp)
 target_link_libraries(${TARGET} PRIVATE common llama ${CMAKE_THREAD_LIBS_INIT})
 target_compile_features(${TARGET} PRIVATE cxx_std_11)
+if(TARGET BUILD_INFO)
+  add_dependencies(${TARGET} BUILD_INFO)
+endif()

examples/save-load-state/save-load-state.cpp

@@ -1,5 +1,6 @@
 #include "common.h"
 #include "llama.h"
+#include "build-info.h"
 
 #include <vector>
 #include <cstdio>
@@ -17,6 +18,8 @@ int main(int argc, char ** argv) {
         return 1;
     }
 
+    fprintf(stderr, "%s: build = %d (%s)\n", __func__, BUILD_NUMBER, BUILD_COMMIT);
+
     if (params.n_predict < 0) {
         params.n_predict = 16;
     }