Define strlcpy only on platforms where it's not available

[okias]

Be smart, do not list platforms and combination which has strlcpy, but detect it.

Right now, we conflict with some variation used on musl-libc on ppc64le. This should resolve it.

Btw. recently released glibc have it (we can forgive Ulrich Drepper now 🤣 )

[okias]

failure example:

ninja: job failed: /usr/bin/g++ -DIRRLICHT_API="" -DUSE_CMAKE_CONFIG_H -Dminetest_EXPORTS -I/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/build_client/src -I/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src -I/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src/script -I/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/lib/irrlichtmt/include -I/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/lib/irrlichtmt/source/Irrlicht -isystem /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/lib/lua/src -isystem /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/lib/gmp -isystem /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/lib/jsoncpp -isystem /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/lib/bitop -isystem /usr/include/freetype2 -isystem /usr/include/AL -Os -fstack-clash-protection -Wformat -Werror=format-security -D_GLIBCXX_ASSERTIONS=1 -D_LIBCPP_ENABLE_THREAD_SAFETY_ANNOTATIONS=1 -D_LIBCPP_ENABLE_HARDENED_MODE=1 -DNDEBUG -Wall -Wextra -Wno-unused-parameter  -pipe -funroll-loops -O3 -fomit-frame-pointer -fno-math-errno -fno-trapping-math -fno-signed-zeros -std=gnu++17 -MD -MT src/CMakeFiles/minetest.dir/porting.cpp.o -MF src/CMakeFiles/minetest.dir/porting.cpp.o.d -o src/CMakeFiles/minetest.dir/porting.cpp.o -c /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src/porting.cpp
In file included from /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src/porting.cpp:70:
/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src/util/string.h:86:8: error: declaration of 'size_t mystrlcpy(char*, const char*, size_t) noexcept' has a different exception specifier
   86 | size_t mystrlcpy(char *dst, const char *src, size_t size) noexcept;
      |        ^~~~~~~~~
In file included from /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src/porting.cpp:26:
/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src/porting.h:88:34: note: from previous declaration 'size_t mystrlcpy(char*, const char*, size_t)'
   88 |         #define strlcpy(d, s, n) mystrlcpy(d, s, n)
      |                                  ^~~~~~~~~
ninja: job failed: /usr/bin/g++ -DIRRLICHT_API="" -DUSE_CMAKE_CONFIG_H -Dminetest_EXPORTS -I/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/build_client/src -I/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src -I/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src/script -I/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/lib/irrlichtmt/include -I/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/lib/irrlichtmt/source/Irrlicht -isystem /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/lib/lua/src -isystem /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/lib/gmp -isystem /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/lib/jsoncpp -isystem /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/lib/bitop -isystem /usr/include/freetype2 -isystem /usr/include/AL -Os -fstack-clash-protection -Wformat -Werror=format-security -D_GLIBCXX_ASSERTIONS=1 -D_LIBCPP_ENABLE_THREAD_SAFETY_ANNOTATIONS=1 -D_LIBCPP_ENABLE_HARDENED_MODE=1 -DNDEBUG -Wall -Wextra -Wno-unused-parameter  -pipe -funroll-loops -O3 -fomit-frame-pointer -fno-math-errno -fno-trapping-math -fno-signed-zeros -std=gnu++17 -MD -MT src/CMakeFiles/minetest.dir/log.cpp.o -MF src/CMakeFiles/minetest.dir/log.cpp.o.d -o src/CMakeFiles/minetest.dir/log.cpp.o -c /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src/log.cpp
In file included from /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src/settings.h:23,
                 from /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src/log.cpp:26:
/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src/util/string.h:86:8: error: declaration of 'size_t mystrlcpy(char*, const char*, size_t) noexcept' has a different exception specifier
   86 | size_t mystrlcpy(char *dst, const char *src, size_t size) noexcept;
      |        ^~~~~~~~~
In file included from /builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src/log.cpp:25:
/builds/okias/aports/community/minetest/src/minetest-8093044f071fc6ad20dbc0a07ba2ef824605fff5/src/porting.h:88:34: note: from previous declaration 'size_t mystrlcpy(char*, const char*, size_t)'
   88 |         #define strlcpy(d, s, n) mystrlcpy(d, s, n)
      |                                  ^~~~~~~~~
ninja: subcommands failed

[okias]

Verified, works now: https://gitlab.alpinelinux.org/okias/aports/-/jobs/1247069