crumbs/builder.py: Fix typo for indefinite article

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
cooker: Fix support for wildcards in bbappend filenames

The 'bbappend in f' incorrectly compares the current recipe with the avaliable
bbappends recipes. This comparsion causes unrequested bbappend files to be
appended, e.g. in the case of 'libgcc_4.8.bb', the bbappends for 'libgcc_4.8.bb'
and 'gcc_4.8.bb' are added to the filelist (because 'gcc_4.8.bb' is contained in
the 'libgcc_4.8.bb' string) which in turn causes the gcc_4.8.bbappend files to
be appended to the libgcc_4.8 recipe.

This should be a 'bbappend == f' to match the previous implementation of this
function, such that if no wildcard is present the recipe names must match
exactly.

This issue was introduced by commit 31bc9af9cd56e7b318924869970e850993fafc5f,
which it related to [YOCTO #5411].

Signed-off-by: Nathan Rossi <nathan.rossi@xilinx.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>