lttoolbox: Document workaround for C++ downgrade

Author: Dave-Allured

textproc/lttoolbox/Portfile

@@ -32,6 +32,11 @@ checksums               rmd160  81acb8547ecebd9a1ca335ae4cd949bd76e8df8c \
                         sha256  7028dbbcda6c49467378d47784092ef8aba9a59d53e78102742d1edb7c5ff21b \
                         size    157342
 
+# 2025 Nov 29:  lttoolbox version 3.8.2:
+# Fails on macos 26 CI when -std=c++23 is enabled.
+# Explicitly downgrade the C++ standard until upstream is fixed.
+# https://github.com/apertium/lttoolbox/issues/206
+
 cmake.set_cxx_standard  yes
 compiler.cxx_standard   2017