Re: gub: I can now completely build lilypond

[Masamichi Hosoda]

> Hi Werner!
>>> But building of lilypond-test fails.
>>>
>>> ./target/linux-64/build/lilypond-git.sv.gnu.org--lilypond.git-master/input/regression/lilypond-book/suffix-tely.texi2pdf.log:
>>>
>>>     /home/gub/NewGub/gub/target/tools/root/usr/bin/texi2dvi: texinfo.tex
>>>     appears to be broken.
>>>     This may be due to the environment variable TEX set to something
>>>     other than (plain) tex, a corrupt texinfo.tex file, or
>>>     to tex itself simply not working.
>>>     etex:
>>>     /home/gub/NewGub/gub/target/linux-64/root/usr/lib/libstdc++.so.6:
>>>     version `CXXABI_1.3.9' not found (required by etex)
>> Obviously another linking path issue: While executing the external TeX
>> binaries, DLL stuff from `target/...' must not be used.
> 
> The problem here is that our texi2* stuff needs LD_LIBRARY_PATH to
> find our DLLs in target/..., but the system's etex binary, executed by
> texi2*, fails on openSuSE Tumbleweed because it is incompatible to
> those libs in target/....
> 
> I think the easiest solution is a simple etex wrapper script in
> tools/root that clears LD_LIBRARY_PATH and then executes the system's
> etex.

texi2dvi / texi2pdf can be specified external program name.
Previously, there was a similar error in XeTeX with texi2pdf.

For XeTeX, we use wrapper scripts.
http://git.savannah.gnu.org/gitweb/?p=lilypond.git;a=blob;f=scripts/build/xetex-with-options.sh
http://git.savannah.gnu.org/gitweb/?p=lilypond.git;a=blob;f=scripts/build/xelatex-with-options.sh

In the LilyPond's makefiles, it is specified as follows.

```
PDFTEX=$(PDFTEX) PDFLATEX=$(PDFLATEX)  ... $(LILYPOND_BOOK)
```

The valiables, PDFTEX and PDFLATEX are set to be
xetex-with-options.sh and xelatex-with-options.sh at configure script.

To avoid the error,
I've added a line to clear LD_LIBRARY_PATH to the scripts in GUB.
https://github.com/gperciva/gub/commit/57d66d1262551c062a3edc85e27ac69748f2f136#diff-94f19c1786c0853ef47371aa55ba2b21

If I understand correctly,
it may be resolved simply by changing LilyPond's makefiles as follows.

```
TEX=$(PDFTEX) PDFTEX=$(PDFTEX) PDFLATEX=$(PDFLATEX)  ... $(LILYPOND_BOOK)
```