gsed,texinfo builds fail on MSYS2 for RTEMS 6

Summary

MSYS2, target arm,aarch64

build command

../source-builder/sb-set-builder --log=l-arm.txt --prefix=/opt/rtems/6.1 6/rtems-arm

build gsed and texinfo has the same error messages.

error message:

RTEMS Source Builder - Set Builder, 6 (c4975f3bc2a9 modified)
Build Set: 6/rtems-arm
Build Set: tools/rtems-default-tools.bset
Build Set: textproc/gsed-internal.bset
config: textproc/gsed.cfg
Build Set: Time 0:00:00.161234
Build Set: Time 0:00:00.167836
Build Set: Time 0:00:00.175380
Traceback (most recent call last):
  File "/home/ZXJ/rtems-source-builder/rtems/../source-builder/sb-set-builder", line 25, in <module>
    sb.setbuilder.run()
  File "/home/ZXJ/rtems-source-builder/source-builder/sb/setbuilder.py", line 812, in run
    b.build(deps, mail=mail)
  File "/home/ZXJ/rtems-source-builder/source-builder/sb/setbuilder.py", line 489, in build
    bs.build(deps, nesting_count, mail)
  File "/home/ZXJ/rtems-source-builder/source-builder/sb/setbuilder.py", line 489, in build
    bs.build(deps, nesting_count, mail)
  File "/home/ZXJ/rtems-source-builder/source-builder/sb/setbuilder.py", line 498, in build
    b = build.build(
        ^^^^^^^^^^^^
  File "/home/ZXJ/rtems-source-builder/source-builder/sb/build.py", line 151, in __init__
    self.macros['buildname'] = short_name(self.macros['name'])
                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ZXJ/rtems-source-builder/source-builder/sb/build.py", line 70, in short_name
    buildname += n[0]
                 ~^^^
IndexError: string index out of range