disable LLD build for cross compiled hosts

[jclulow]

At present, the LLD build requested by the --enable-lld configure option
appears to make direct use of the "llvm-config" binary built as part of
the LLVM build. For cross built LLVM, the "llvm-config" binary produced
is intended to run on the target system, so it seems like this cannot
work as intended today. Disable the LLD build for cross compiled hosts,
while continuing to allow --enable-lld to build a native LLD for use by
targets like Fuchsia that expect to use it for linking.

[rust-highfive]

r? @Mark-Simulacrum

(rust_highfive has picked a reviewer for you, use r? to override)

[jclulow]

NOTE: This was chiefly motivated by bumping into this issue as part of work on #71272.

[jclulow]

Hi! I'd like to continue moving on #71272. Would somebody be able to take a look at this PR, and tell me if my analysis is incorrect or if there's a better way I could work on fixing this? Thanks.

[mati865]

#71486 should properly fix the issue. I'll test it and report later today.

[jclulow]

Cool! Thank you!

[mati865]

#71486 is now merged and the binary looks correct to me:

$ readelf -V obj/build/x86_64-unknown-illumos/lld/bin/lld
...
Version needs section '.gnu.version_r' contains 4 entries:
 Addr: 0x0000000000411308  Offset: 0x011308  Link: 4 (.dynstr)
  000000: Version: 1  File: libdl.so.1  Cnt: 1
  0x0010:   Name: SUNW_0.8  Flags: none  Version: 14
  0x0020: Version: 1  File: librt.so.1  Cnt: 3
  0x0030:   Name: SUNW_1.1  Flags: none  Version: 16
  0x0040:   Name: SUNW_1.2  Flags: none  Version: 13
  0x0050:   Name: SUNW_0.7  Flags: none  Version: 11
  0x0060: Version: 1  File: libm.so.2  Cnt: 2
  0x0070:   Name: SUNW_1.1  Flags: none  Version: 7
  0x0080:   Name: SUNW_1.2  Flags: none  Version: 3
  0x0090: Version: 1  File: libc.so.1  Cnt: 10
  0x00a0:   Name: SUNW_1.23  Flags: none  Version: 17
  0x00b0:   Name: SYSVABI_1.3  Flags: none  Version: 15
  0x00c0:   Name: SUNWprivate_1.1  Flags: none  Version: 12
  0x00d0:   Name: ILLUMOS_0.12  Flags: none  Version: 10
  0x00e0:   Name: SUNW_0.9  Flags: none  Version: 9
  0x00f0:   Name: SUNW_1.22  Flags: none  Version: 8
  0x0100:   Name: SUNW_1.1  Flags: none  Version: 6
  0x0110:   Name: ILLUMOS_0.8  Flags: none  Version: 5
  0x0120:   Name: SUNW_1.18  Flags: none  Version: 4
  0x0130:   Name: SUNW_0.7  Flags: none  Version: 2

[jclulow]

Thanks @mati865! I have confirmed that #71486 appears to solve the problem for me. After dropping this patch and rebasing on what is now in master, my cross build of the illumos toolchain on a Linux host (for #71272) works as well.