While this isn't a supported build configuration, some build
systems need to build without going through our autotools steps,
so defaulting to something sane may make it easier to build.
Specifically, this fixes the inability to build
rust-bitcoinconsensus on some non-x86 platforms. It needs to build
without our autotools/configure steps to ensure correct compile
args are passed from the rust build system to gcc. Converting the
args from the rust build system to gcc would be a lot of
unmaintainable work.
- Detect endian instead of stopping configure on big-endian
- Add `byteswap.h` and `endian.h` header for compatibility with
Windows and other operating systems that don't come with them
- Update `crypto/common.h` functions to use compat
endian header
Backwards-compatibility for libstdc++ is not limited to straightforward abi
changes. Symbol visibility also needs to be taken into consideration, and
that really can't be addressed simply.
Instead, just static-link libstdc++ for backwards-compat.
bitcoin-config.h moved, but the old file is likely to still exist when
reconfiguring or switching branches. This would've caused files to not rebuild
correctly, and other strange problems.
Make the path explicit so that the old one cannot be found.
Core libs use config/bitcoin-config.h.
Libs (like crypto) which don't want access to bitcoin's headers continue
to use -Iconfig and #include bitcoin-config.h.
glibc/libstdc++ have added new symbols in later releases. When running a new
binary against an older glibc, the run-time linker is unable to resolve the
new symbols and the binary refuses to run.
This can be fixed by adding our own versions of those functions, so that the
build-time linker does not emit undefined symbols for them.
This enables our binary releases to work on older Linux distros, while not
incurring the downsides of a fully static binary.