Support non-zero minutes in the timestamp offset for JSON.

[haberman]

This is to address protocolbuffers/protobuf#8071

[haberman]

I'm not sure where this compile failure came from, but it has nothing to do with this PR:

ERROR: /Volumes/BuildData/tmpfs/tmp/bazel/external/com_google_absl/absl/base/BUILD.bazel:192:11: Compiling absl/base/internal/thread_identity.cc failed: (Exit 1): wrapped_clang failed: error executing command external/local_config_cc/wrapped_clang '-D_FORTIFY_SOURCE=1' -fstack-protector -fcolor-diagnostics -Wall -Wthread-safety -Wself-assign -fno-omit-frame-pointer -g0 -O2 '-D_FORTIFY_SOURCE=1' -DNDEBUG ... (remaining 41 argument(s) skipped)

Use --sandbox_debug to see verbose messages from the sandbox wrapped_clang failed: error executing command external/local_config_cc/wrapped_clang '-D_FORTIFY_SOURCE=1' -fstack-protector -fcolor-diagnostics -Wall -Wthread-safety -Wself-assign -fno-omit-frame-pointer -g0 -O2 '-D_FORTIFY_SOURCE=1' -DNDEBUG ... (remaining 41 argument(s) skipped)

Use --sandbox_debug to see verbose messages from the sandbox
clang: error: unknown argument: '-fdebug-compilation-dir'
clang: warning: .: 'linker' input unused [-Wunused-command-line-argument]