comments explaining build version constants in build_version.cc

Added comments to explain the purpose of constants in the build_version code.

- Explained that `rocksdb_build_git_sha` is used to store the Git SHA of the build.
- Clarified that `rocksdb_build_git_date` stores the date of the latest Git commit.
- Added details about `rocksdb_build_compile_date` and its typical usage.

These comments improve code readability and provide context for developers or maintainers.

deps/rocksdb/build_version.cc

@@ -1,4 +1,16 @@
 #include "rocksdb/util/build_version.h"
+
+// String constant to store the Git SHA of the current build.
+// Typically, this would contain the hash of the latest commit in the Git repository.
+// Here, it is set to "None," indicating that this information is not available or not provided.
 const char* rocksdb_build_git_sha = "rocksdb_build_git_sha:None";
+
+// String constant to store the date of the latest Git commit.
+// In a typical build, this would reflect the date of the commit associated with the Git SHA.
+// Here, it is set to "None," indicating that the date information is not available or not provided.
 const char* rocksdb_build_git_date = "rocksdb_build_git_date:None";
+
+// String constant to store the compilation date of the RocksDB library.
+// This would normally be set during the build process to the current date and time of compilation.
+// The value "None" suggests that this information was not included in the build.
 const char* rocksdb_build_compile_date = "None";