clang: -shared -fsanitize=undefined doesn't link with libubsan

[stsp]

$ gcc -shared -o libex.so example.c -fsanitize=undefined
$ ldd libex.so
	linux-vdso.so.1 (0x000079ecce133000)
	libubsan.so.1 => /lib/x86_64-linux-gnu/libubsan.so.1 (0x000079eccda00000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x000079eccd600000)
	libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x000079eccd200000)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x000079ecce0df000)
	/lib64/ld-linux-x86-64.so.2 (0x000079ecce135000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x000079eccd913000)

$ clang -shared -fsanitize=undefined -o libex.so example.c
$ ldd libex.so
	linux-vdso.so.1 (0x000077ad748b4000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x000077ad74600000)
	/lib64/ld-linux-x86-64.so.2 (0x000077ad748b6000)

As the result, when used with
-Wl,--no-undefined this breaks
on clang, but works properly with
gcc.

[llvmbot]

@llvm/issue-subscribers-clang-driver

Author: Stas Sergeev (stsp)

``` $ gcc -shared -o libex.so example.c -fsanitize=undefined $ ldd libex.so linux-vdso.so.1 (0x000079ecce133000) libubsan.so.1 => /lib/x86_64-linux-gnu/libubsan.so.1 (0x000079eccda00000) libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x000079eccd600000) libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x000079eccd200000) libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x000079ecce0df000) /lib64/ld-linux-x86-64.so.2 (0x000079ecce135000) libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x000079eccd913000)

$ clang -shared -fsanitize=undefined -o libex.so example.c
$ ldd libex.so
linux-vdso.so.1 (0x000077ad748b4000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x000077ad74600000)
/lib64/ld-linux-x86-64.so.2 (0x000077ad748b6000)

As the result, when used with
`-Wl,--no-undefined` this breaks
on clang, but works properly with
gcc.
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