Error when `FFMPEG_PKG_CONFIG_PATH` not exist #302

Job	Run time
build_static_and_test_ubuntu	5m 36s
build_dynamic_and_test_ubuntu	1m 44s
build_dynamic_and_test_windows_pre	3m 39s
build_dynamic_and_test_macos	4m 3s
build_static_and_test_ubuntu_with_system_ffmpeg	1m 27s
docs_rs_check	1m 29s
build_with_vcpkg_ffmpeg_windows (x86_64-pc-windows-msvc, x64-windows-static, -Ctarget-feature=+cr...	27m 14s
rust_clippy_check_ubuntu	4m 57s
build_with_vcpkg_ffmpeg_windows (x86_64-pc-windows-msvc, x64-windows-static-md)	26m 20s
rust_clippy_check_windows	26m 21s
build_with_vcpkg_ffmpeg_windows (x86_64-pc-windows-msvc, x64-windows, true)	27m 29s
rustfmt_check (macos-latest)	22s
build_with_vcpkg_ffmpeg_windows (i686-pc-windows-msvc, x86-windows-static, -Ctarget-feature=+crt-...	26m 0s
rustfmt_check (windows-latest)	43s
build_with_vcpkg_ffmpeg_windows (i686-pc-windows-msvc, x86-windows-static-md)	25m 33s
rustfmt_check (ubuntu-latest)	10s
build_with_vcpkg_ffmpeg_windows (i686-pc-windows-msvc, x86-windows, true)	25m 36s
build_dynamic_and_test_windows	1m 44s
	3h 30m 27s

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