The lyx dependencies are incorrect.
Currently the PKGBUILD has the following line:
depends=('gcc' 'x-server' 'xforms' 'libjpeg')

I would recommend changing that line to:
depends=('x-server' 'xforms' 'tetex' 'python' 'perl' 'imagemagick')

tetex is VITAL to lyx working properly. The lyx webpage (http://www.lyx.org/download/related.php3) says that python is also a requirement. The same site also says that imagemagick is a requirement, and that also satisfies the libjpeg requirement. gcc is also already satisfied by the said requirements. perl is recommended as an optional requirement on the lyx page above. The following quote is from that page:
"Note that reLyX is bundled with LyX, but is only installed if Perl is found."

I would also recommend the following change:
depends=('x-server' 'qt' 'tetex' 'python' 'perl' 'imagemagick')

The only difference with the above line is replcing xforms with qt. xforms is a rarely used toolkit and the fonts look terrible. lyx with qt looks MUCH MUCH MUCH better.
The following is a build statement that configures with qt:
build() {
cd $startdir/src/lyx-$pkgver
./configure --prefix=/usr \
--with-qt-dir=/opt/qt \
--with-qt-includes=/opt/qt/include \
--with-qt-libraries=/opt/qt/lib \
--with-frontend=qt
make || return 1
make DESTDIR=$startdir/pkg install
}