Setting LD environment explicitly to the ld.lld location

[tanshihaj]

Currently since environment variable LD not set, autotools takes host system's ld located somewhere in /usr/bin/ld as linker:

...
checking for ld used by /Users/username/.conan/data/android-ndk/r18/theodelrieu/testing/package/089e0bdb9fdcbe66e71ad399fd4591508697382b/toolchains/llvm/prebuilt/darwin-x86_64/bin/clang... /usr/bin/ld
checking if the linker (/usr/bin/ld) is GNU ld... no
...
checking for /usr/bin/ld option to reload object files... -r
...
checking whether the /Users/kamil/.conan/data/android-ndk/r18/theodelrieu/testing/package/089e0bdb9fdcbe66e71ad399fd4591508697382b/toolchains/llvm/prebuilt/darwin-x86_64/bin/clang linker (/usr/bin/ld) supports shared libraries... no
...
checking if the linker (/usr/bin/ld) is GNU ld... no
...

Setting LD manually solve this issue.

[theodelrieu]

Thanks!