Originally, I thought that the dSYM bundle has to reside side-by-side
with the binary it carries the debugging information for. However, it
turns out macOS is clever enough that it auto-searches for matching
dSYM bundle based on the embedded UUID of the binary.
To verify this, run this on your macOS:
```
mdfind "com_apple_xcode_dsym_uuids == <UUID from LC_UUID>"
```
See [here] for more info.
[here]: https://developer.apple.com/documentation/xcode/adding-identifiable-symbol-names-to-a-crash-report
* `-lc++` now implies `-lc`.
* `-lunwind` is now pulled out into a separate `link_libunwind` flag in
the frontend driver code. This allows a project to request zig to
provide libunwind even if the default situation that causes it to be
implicitly added, is not active.
* build.zig: ask for -lunwind when building the self-hosted compiler on
Linux. Otherwise we get linker errors with unresolved symbols to
libunwind.
5ac91794cce8bd53916a378815be01e4365d53d9 made Zig link against the
system libc when targeting the native C ABI. However this made it stop
putting libunwind.a on the linker line when it needed to sometimes,
causing undefined symbols when linking against C++ code.
Previously, I mistakenly assumed that offset of the relocation
is enough when calculating relative offset of the target from the
source target section base address in case of section-based relocs
on x86_64. While this is true for `__TEXT,__text` section which
always starts at 0x0 in object files, this is absolutely not true
for `__TEXT,__StaticInit` section which will have nonzero base
address hence resulting in incorrect displacement calculations for
SIGNED relocs.
* UTF16 gets its own section, `__TEXT,__ustring`
* TLV data and bss sections have to aligned to the same max alignment
according to Apple rdar comment in the latest ld64
