./gradlew assemble fails due to missing file when the file clearly exists

[BG864]

I'm trying to build JPostal as described in this link using the following command:

./gradlew assemble

However, the command produces the following output claiming the file /../tcl-tea.m4 does not exist when it clearly does:

:buildJniLibaclocal-1.16: error: aclocal: file '/x/Program Files/Msys64/usr/share/aclocal/tcl-tea.m4' does not exist
autoreconf-2.71: error: aclocal failed with exit status: 1
./build.sh: line 3: ./configure: No such file or directory
make: *** No rule to make target 'install'.  Stop.
 FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':buildJniLib'.
> Process 'command 'sh'' finished with non-zero exit value 2

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

Total time: 3.387 secs

I can clearly see a file named tcl-tea.m4 in the directory: C:\x\Program Files\Msys64\usr\share\aclocal

See the screenshot below:

If the file clearly exists, why am I getting this error? Why is the file being discriminated against?