This is a flat buffers inspired format that allows fast
mmaped access to the data with low overhead, signature support
and relatively good forward support.

Most notably this happens after blank database is initialized with --initdb,
but can happen also in other conditions.

The error checking changes modified behaviour if the file does not exist.
Explicitly check for ENOENT and ignore it. But the behaviour is improved
from earlier as now e.g. EPERM will be detected and reported correctly.

Fixes #10679

Fixes: 6da3e8eb15 "istream, archive, db: convert db and tar function to use istream"

Some screen size are quite small. For example, the default phosh
terminal is less than 50 character wide on Pinephone. This lowers the minimum
loading bar size to 25 characters.

For comparison, 25 character wide is just as wide as "apk add firefox
linux-lts" without the quotes.

Here's a bad picture to illustrate the result
gitlab.alpine.org/uploads/48c20f746fbf685b62b6bd73585ecbf2/pinephone-phosh.png

fixes #10677

src/apk_defines.h:152:15: error: unknown type name 'uint32_t'
 static inline uint32_t get_unaligned32(const void *ptr)
               ^~~~~~~~

- always create .so and .a with the apk libary code
- create .pc file
- install headers and above mentioned files

Maintainers edit: merged commits, cleaned up sed script logic,
and few other minor fixes.

- do not do unaligned accesses on non-x86 hardware
- clean up the code a little bit