[BUG] Check LC_CTYPE to set UTF-8 locale

[lcheylus]

On some OS (especially on OpenBSD), locale are defined only via LC_CTYPE (export LC_CTYPE=en_US.UTF-8) => see https://www.openbsd.org/faq/faq10.html#locales

With this configuration, no UTF-8 locale is detected at start.

Reproduction

• Define only LC_CTYPE=en_US.UTF-8 for locale

$ unset LANG
$ unset LC_ALL

$ locale
LANG=
LC_COLLATE="C"
LC_CTYPE=en_US.UTF-8
LC_MONETARY="C"
LC_NUMERIC="C"
LC_TIME="C"
LC_MESSAGES="C"
LC_ALL=

• Error when startting btop:

$ bin/btop
ERROR: No UTF-8 locale detected!
Use --utf-force argument to force start if you're sure your terminal can handle it.

Expected behavior

UTF-8 locale is checked in src/btop.cpp (line 915...). In line 923, I propose to check also LC_CTYPE variable value for UTF-8:

for (const auto loc_env : array{"LANG", "LC_ALL"})

Info:

• btop++ version: 1.3.0 (last Git version)
• Binary: self compiled
• Compiler and version: clang v16
• Architecture: x86_64
• Platform: OpenBSD
• Terminal used: Kitty