internal.c: error: incompatible integer to pointer conversion

[Schamschula]

While updating certbot for MacPorts, I noticed that augeas, which is a dependency of certbot-apache was failing to build under macOS 15 (Sequoia). On closer examination I found the following build issue:

:info:build libtool: compile:  /usr/bin/clang -DHAVE_CONFIG_H -I. -I.. -I/opt/local/include -isysroot/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.sdk -std=gnu99 -Wall -Wformat -Wformat-security -Wmissing-prototypes -Wnested-externs -Wpointer-arith -Wextra -Wshadow -Wcast-align -Wwrite-strings -Waggregate-return -Wstrict-prototypes -Winline -Wredundant-decls -Wno-sign-compare -fexceptions -fasynchronous-unwind-tables -I ../gnulib/lib -I ../gnulib/lib -I/opt/local/include/libxml2 -pipe -Os -isysroot/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.sdk -arch arm64 -MT internal.lo -MD -MP -MF .deps/internal.Tpo -c internal.c  -fno-common -DPIC -o .libs/internal.o
:info:build internal.c:436:12: error: incompatible integer to pointer conversion returning 'int' from a function with result type 'const char *' [-Wint-conversion]
:info:build   436 |     return strerror_r(errnum, buf, len);
:info:build       |            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~info:build 1 error generated.