Add empty build.h file to repo

.gitignore

@@ -8,7 +8,6 @@ firmware*
 .gcc-flags.json
 .sconsign.dblite
 credentials.h
-build.h
 node_modules
 code/utils
 custom.h

code/.gitignore

@@ -4,6 +4,5 @@
 .piolibdeps
 .vscode/c_cpp_properties.json
 core_version.h
-build.h
 .pioenvs
 .piolibdeps

code/espurna/config/build.h

@@ -0,0 +1,3 @@
+// DO NOT EDIT THIS FILE MANUALLY
+// This file is modified by PlatformIO
+#define APP_BUILD_FLAGS ""