Make SRFI test program writing more reliable

[Retropikzel]

This pull request is related to #1078. It does not fix the whole thing but is a step into that direction.

Part of the problem for example with Kawa is that sometimes the SRFI checking code is not fully written into the tempfile.

This is weird as it is Chibi who is doing the writing.

Old implementation here:

chibi-scheme/lib/chibi/snow/commands.scm

Line 1894 in da20079

(define (native-srfi-support impl cfg)

First putting the strings into list and then writing them out one by one seems more reliable than writing things out in a loop inside with-output-to-file.

[Retropikzel]

Current main:
snow-chibi install --impls=kawa srfi.1

Can't find package: (srfi 1)

Tempfile writing fails, thinks Kawa does not support any SRFI's.

With changes in this pull request.

snow-chibi install --impls=kawa srfi.1 silently not installed.

snow-chibi install --impls=kawa srfi.39 installed, as there is candidate available. Will be address in another pull request.

[Retropikzel]

Thank you!