Eliminate use of cat and subshells in patching.
The previous code takes the first field of PKG_BUILD, using a space
as the delimiter. PKG_BUILD used to be generated using 'ls' at least
as of before commit ef8e871d3c in 2013.
Today, PKG_BUILD is a set path, without spaces.
Signed-off-by: Ian Leonard <antonlacon@gmail.com>
9326345a6e