Manually adding `gfortran` to `%PATH%` in AppVeyor.
mkdir build
cd build
+:: NOTE: This "should be" the following
+::
+:: IF "%APPVEYOR%"=="True" (
+:: IF "%ARCH%"=="32" (
+:: set PATH=%PATH%;C:\mingw-w64\i686-6.3.0-posix-dwarf-rt_v5-rev1\mingw32\bin
+:: ) ELSE (
+:: set PATH=%PATH%;C:\mingw-w64\x86_64-8.1.0-posix-seh-rt_v6-rev0\mingw64\bin
+:: )
+:: )
+::
+:: OR
+::
+:: set PATH=%PATH%;C:\mingw-w64\x86_64-8.1.0-posix-seh-rt_v6-rev0\mingw64\bin;C:\mingw-w64\i686-6.3.0-posix-dwarf-rt_v5-rev1\mingw32\bin
+::
+:: but the pre-processing of `bld.bat` causes issues with the indents.
+
:: Workaround for `git bash`; CMake errors with
:: For MinGW make to work correctly sh.exe must NOT be in your path.
:: when using the "MinGW Makefiles" generator.
