opendetex 2.8.6 failed to build on osx

[chenrui333]

relates to https://github.com/Homebrew/homebrew-core/pull/52945

GHA run link, https://github.com/Homebrew/homebrew-core/runs/579966775

build failure log

``` �[34m==>�[0m �[1mbrew install --verbose --build-bottle opendetex�[0m /usr/bin/sandbox-exec -f /private/tmp/homebrew20200412-27706-1tz1p46.sb nice ruby -W0 -I $LOAD_PATH -- /usr/local/Homebrew/Library/Homebrew/build.rb /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/opendetex.rb --build-bottle --verbose �[34m==>�[0m �[1mDownloading https://github.com/pkubowicz/opendetex/releases/download/v2.8.6/opendetex-2.8.6.tar.bz2�[0m Already downloaded: /Users/brew/Library/Caches/Homebrew/downloads/b734c8e3d2c019b9fb8f5a95c7735958b3fcfbe3f4b56418d9d38e2154855a6f--opendetex-2.8.6.tar.bz2 �[34m==>�[0m �[1mVerifying b734c8e3d2c019b9fb8f5a95c7735958b3fcfbe3f4b56418d9d38e2154855a6f--opendetex-2.8.6.tar.bz2 checksum�[0m tar xof /Users/brew/Library/Caches/Homebrew/downloads/b734c8e3d2c019b9fb8f5a95c7735958b3fcfbe3f4b56418d9d38e2154855a6f--opendetex-2.8.6.tar.bz2 -C /private/tmp/d20200412-27707-c34c8n cp -pR /private/tmp/d20200412-27707-c34c8n/INSTALL /private/tmp/opendetex-20200412-27707-18shzlw/INSTALL cp -pR /private/tmp/d20200412-27707-c34c8n/ChangeLog /private/tmp/opendetex-20200412-27707-18shzlw/ChangeLog cp -pR /private/tmp/d20200412-27707-c34c8n/Makefile /private/tmp/opendetex-20200412-27707-18shzlw/Makefile cp -pR /private/tmp/d20200412-27707-c34c8n/detex.c /private/tmp/opendetex-20200412-27707-18shzlw/detex.c cp -pR /private/tmp/d20200412-27707-c34c8n/detex.l /private/tmp/opendetex-20200412-27707-18shzlw/detex.l cp -pR /private/tmp/d20200412-27707-c34c8n/README /private/tmp/opendetex-20200412-27707-18shzlw/README cp -pR /private/tmp/d20200412-27707-c34c8n/COPYRIGHT /private/tmp/opendetex-20200412-27707-18shzlw/COPYRIGHT cp -pR /private/tmp/d20200412-27707-c34c8n/detex.o /private/tmp/opendetex-20200412-27707-18shzlw/detex.o cp -pR /private/tmp/d20200412-27707-c34c8n/detex.h /private/tmp/opendetex-20200412-27707-18shzlw/detex.h cp -pR /private/tmp/d20200412-27707-c34c8n/detex.1 /private/tmp/opendetex-20200412-27707-18shzlw/detex.1 chmod -Rf +w /private/tmp/d20200412-27707-c34c8n �[34m==>�[0m �[1mmake�[0m clang -O -DVERSION=\"2.8.6\" -Wall -o detex detex.o -ll Undefined symbols for architecture x86_64: "_yylex", referenced from: _main in libl.a(libmain.o) ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation) make: *** [detex] Error 1 ```

[pkubowicz]

Opendetex is continuously built on OS X: https://travis-ci.org/github/pkubowicz/opendetex/jobs/673731389

I think your build environment lacks flex package.

[chenrui333]

Actually the build passed with 2.8.8 release build, https://github.com/Homebrew/homebrew-core/pull/56636, closing this issue for now. Thanks!