The bug was introduced dad6817f ("Use the R6RS I/O API in
`write-bytecode'.").
* module/language/assembly/compile-bytecode.scm
(write-bytecode)[write-string]: Rename to...
[write-latin1-string]: ... this. Add the `write-loader-len' call.
Write each character individually instead of using `string->utf8'.
[write-loader]: Remove.
* test-suite/tests/asm-to-bytecode.test ("compiler")[load-string "æ"]:
New test.