Add env for using the bundled protoc for building tiflash-proxy

[JaySon-Huang]

What problem does this PR solve?

Issue Number: close #4460

Problem Summary:

# protoc is installed system-wide but not runnable under my own envs
>  which protoc
/usr/local/bin/protoc
>  protoc
protoc: error while loading shared libraries: libprotoc.so.3.8.0.0: cannot open shared object file: No such file or directory

# when building tiflash proxy, it can not use the protoc in `${BUILD_DIR}/protobuf-cmake/protoc`
# and get error
>  ninja tiflash_proxy
...
+ cargo build --no-default-features --features ' portable sse protobuf-codec test-engines-rocksdb cloud-aws cloud-gcp' --release
   Compiling raft-proto v0.6.0-alpha (GitHub - tikv/raft-rs: Raft distributed consensus algorithm implemented in Rust.)
   Compiling kvproto v0.0.2 (https://github.com/pingcap/kvproto.git?rev=706fcaf286c8dd07ef59349c089f53289a32ce4c#706fcaf2)
   Compiling tipb v0.0.1 (GitHub - pingcap/tipb: TiDB protobuf)
error: failed to run custom build command for `raft-proto v0.6.0-alpha (GitHub - tikv/raft-rs: Raft distributed consensus algorithm implemented in Rust.)`
Caused by:
  process didn't exit successfully: `/DATA/disk1/jaysonhuang/tics/contrib/tiflash-proxy/target/release/build/raft-proto-2d9d1f476dd22edf/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', /DATA/disk1/jaysonhuang/.cargo/registry/src/github.com-1ecc6299db9ec823/protobuf-build-0.12.3/src/protobuf_impl.rs:48:71
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...
error: build failed
make[1]: *** [build] Error 101
make[1]: Leaving directory `/DATA/disk1/jaysonhuang/tics/contrib/tiflash-proxy'
make: *** [release] Error 2
ninja: build stopped: subcommand failed.

What is changed and how it works?

Set the env PROTOC and PROTOC_INCLUDE while building tiflash-proxy

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• SchrodingerZhu
• SeaRise

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[JaySon-Huang]

/merge

[ti-chi-bot]

@JaySon-Huang: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 41f089c

[zanmato1984]

LGTM

[zanmato1984]

What does protoc have anything to do with tiflash proxy?

[JaySon-Huang]

@zanmato1984 tiflash-proxy need protoc to compile tipb kvproto for its Rust codes

[zanmato1984]

LGTM

[sre-bot]

Coverage for changed files

no c/c++ source change detected

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
17049      9575             43.84%    191778  96985        49.43%

full coverage report (for internal network access only)

[sre-bot]

Coverage for changed files

no c/c++ source change detected

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
17049      9576             43.83%    191778  97025        49.41%

full coverage report (for internal network access only)