intel compiler toolchain on CentOS - linking against custom glibc

Hello, all.

I am trying to get the the 2019 release working on centos6.

The system ships with gcc 4.4 and old glibc, which do not have full support for c++11. Instead, I compiled and installed gcc 5.5 and glibc 2.23 through linuxbrew, and I am trying to compile with `icpc` with linuxbrew's `gcc` toolchain.

However, when compiling, icpc insists on using system versions of glibc:

> icpc -cxxlib=/home/user/.linuxbrew/ -std=c++11 hello.cpp -o hello
ld: /home/user/.linuxbrew/Cellar/gcc/5.5.0_4/bin/../lib/gcc/x86_64-unknown-linux-gnu/5.5.0/../../..//libstdc++.so: 
undefined reference to `memcpy@GLIBC_2.14'

Instead, I expect it to resolve to glibc 2.23, as installed with homebrew.

`icpc` seems to know about my 5.5 executable:

> icpc -v
icpc version 19.0.0.117 (gcc version 5.5.0 compatibility)

Further, if I explicitly include `~/.linuxbrew/lib` as a linking directory, `ld` succeeds, but the runtime library lookup fails, as it appears that the linker uses system libraries:

> icpc -cxxlib=/home/user/.linuxbrew/ -std=c++11 -L ~/.linuxbrew/lib hello.cpp -o hello
> ldd hello
./hello: /usr/lib64/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by ./hello)
	linux-vdso.so.1 =>  (0x00007f1781c4c000)
	libstdc++.so.6 => /usr/lib64/libstdc++.so.6 (0x0000003caee00000)
	libm.so.6 => /lib64/libm.so.6 (0x0000003ca5200000)
	libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x0000003caea00000)
	libc.so.6 => /lib64/libc.so.6 (0x0000003ca4e00000)
	libdl.so.2 => /lib64/libdl.so.2 (0x0000003ca5a00000)
	/lib64/ld-linux-x86-64.so.2 (0x0000003ca4a00000)

I would expect that providing `-cxxlib=<path>` and `-L <inlclude>` should link against libraries in `/home/user/.linuxbrew/lib`.

What am I missing?

Thank you!