Fix protoc searching with non-imported protobuf::protoc target. (#2362) #76

Job	Run time
CMake clang 14 (maintainer mode, abiv2)	20m 49s
CMake test (with abseil)	7m 35s
CMake clang 14 (maintainer mode, async)	20m 27s
CMake gcc 12 (maintainer mode, async)	10m 50s
CMake msvc (maintainer mode)	11m 18s
CMake test (without otlp-exporter)	6m 56s
CMake test (without otlp-exporter and with async export)	6m 57s
CMake do not install test (with otlp-exporter)	29m 39s
CMake gcc 12 (maintainer mode, sync)	13m 23s
CMake install test (with abseil)	7m 52s
CMake test (with modern protobuf,grpc and abseil)	29m 36s
CMake test (with opentracing-shim)	8m 51s
CMake test (build shared libraries with otlp-exporter and static gRPC)	20m 37s
CMake test (with otlp-exporter)	21m 7s
CMake C++14 test(GCC)	6m 1s
CMake C++17 test(GCC)	7m 55s
CMake C++20 test(Clang with libc++)	11m 8s
CMake C++20 test(GCC)	14m 56s
Bazel asan config	1m 3s
Bazel noexcept	19m 47s
Bazel nortti	26m 22s
Bazel on MacOS	16m 40s
Bazel	23m 39s
Bazel with async export	19m 59s
Bazel tsan config	20m 51s
Bazel valgrind	23m 2s
Bazel with external abseil	19m 41s
Benchmark	12m 45s
CMake clang 14 (maintainer mode, sync)	23m 13s
Code coverage	13m 14s
Copyright	11s
DocFX check	37s
Format	20s
markdown-lint	7s
misspell	7s
Plugin -> CMake	1m 48s
CMake -> exporter proto	18m 39s
Bazel Windows	39m 30s
Plugin -> CMake Windows	9m 6s
CMake (With async export) -> exporter proto	17m 49s
CMake -> exporter proto (Build as DLL)	20m 57s
	9h 45m 24s

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