ARROW-5498: [C++][CI] Fix Flatbuffers related error with MinGW
ARROW-5498: [C++][CI] Fix Flatbuffers related error with MinGW

We should send a pull request that adds -DCMAKE_BUILD_TYPE=Release to
https://github.com/msys2/MINGW-packages/blob/master/mingw-w64-flatbuffers/PKGBUILD
.

Author: Sutou Kouhei <kou@clear-code.com>

Closes #4465 from kou/cpp-appveyor-flatbuffers and squashes the following commits:

76f49a6a6 <Sutou Kouhei>  Fix Flatbuffers related error with MinGW

renesugar/arrow,wesm/arrow,icexelloss/arrow,renesugar/arrow,kou/arrow,wesm/arrow,apache/arrow,majetideepak/arrow,xhochy/arrow,icexelloss/arrow,majetideepak/arrow,icexelloss/arrow,laurentgo/arrow,icexelloss/arrow,cpcloud/arrow,wesm/arrow,icexelloss/arrow,majetideepak/arrow,majetideepak/arrow,cpcloud/arrow,majetideepak/arrow,cpcloud/arrow,icexelloss/arrow,xhochy/arrow,kou/arrow,apache/arrow,kou/arrow,renesugar/arrow,majetideepak/arrow,renesugar/arrow,laurentgo/arrow,cpcloud/arrow,kou/arrow,majetideepak/arrow,apache/arrow,renesugar/arrow,laurentgo/arrow,renesugar/arrow,apache/arrow,kou/arrow,apache/arrow,wesm/arrow,kou/arrow,kou/arrow,wesm/arrow,apache/arrow,kou/arrow,icexelloss/arrow,wesm/arrow,laurentgo/arrow,xhochy/arrow,majetideepak/arrow,apache/arrow,cpcloud/arrow,xhochy/arrow,laurentgo/arrow,icexelloss/arrow,renesugar/arrow,laurentgo/arrow,xhochy/arrow,cpcloud/arrow,cpcloud/arrow,apache/arrow,xhochy/arrow,apache/arrow,renesugar/arrow,xhochy/arrow,cpcloud/arrow,icexelloss/arrow,cpcloud/arrow,laurentgo/arrow,kou/arrow,majetideepak/arrow,xhochy/arrow,icexelloss/arrow,cpcloud/arrow,majetideepak/arrow,xhochy/arrow,kou/arrow,renesugar/arrow,xhochy/arrow,majetideepak/arrow,xhochy/arrow,laurentgo/arrow,kou/arrow,laurentgo/arrow,apache/arrow,wesm/arrow,wesm/arrow,cpcloud/arrow,laurentgo/arrow,xhochy/arrow,renesugar/arrow,wesm/arrow,kou/arrow,laurentgo/arrow,renesugar/arrow,renesugar/arrow,laurentgo/arrow,majetideepak/arrow,apache/arrow,cpcloud/arrow,kou/arrow,wesm/arrow,icexelloss/arrow,icexelloss/arrow,renesugar/arrow,majetideepak/arrow,laurentgo/arrow,laurentgo/arrow,apache/arrow,renesugar/arrow,wesm/arrow,wesm/arrow,wesm/arrow,majetideepak/arrow,majetideepak/arrow,xhochy/arrow,kou/arrow,xhochy/arrow,wesm/arrow,apache/arrow,icexelloss/arrow,cpcloud/arrow,renesugar/arrow,cpcloud/arrow,laurentgo/arrow,icexelloss/arrow,xhochy/arrow,apache/arrow