The Makefile function `version_is_greater_or_equal` is used to check if
a version of GNU Make is at least the required one. However, it has
the built-in assumption the version numbers have to format x.y.z,
but Alpine Linux currently ships GNU Make 4.4. This results in
`$(call _pad_number,3,)` which runs `printf '$03d' ''` in the shell,
which is not valid.
This fixes the issue by making `_pad_number` more robust by fall back to
printing `0` with the given padding, if the number given to print is
empty.
The escape codes and special chars now live in their own module. The
color module is only concerned with detecting whether to use colors or
not.
Additional variables are defined with hard a coded ESC char, a tab and a
newline. This removes the need for echo or printf.
Add make only function to convert strings to lowercase and uppercase.
This can replace the `$(shell echo $(var) | tr 'a-z-' 'A-Z_')` pattern.
Using the 'make' implementation results in being around 100 times faster.
A call to `$(ensure_value x,y)` will fail with message y if x is empty, and
otherwise return x. This can be useto write more compact makefiles, while still
producing friendly error messages.
