Remove libcpp_is_static

This change makes libc++ a shared_library iff is_component_build=true, just like
all other components.  This has the advantage that the RPATH doesn't need to be
set in sanitizer (non-component) builds just so binaries can find libc++.so.
This CL also changes RPATH to be set iff is_component_build=true.

Needs buildtools CL:
https://chromium-review.googlesource.com/c/chromium/buildtools/+/1142370

TBR=dpranke,jochen
R=thakis
BUG=850682
CQ_INCLUDE_TRYBOTS=luci.chromium.try:linux_chromium_msan_rel_ng;master.tryserver.chromium.linux:linux_chromium_ubsan_rel_ng;luci.chromium.try:linux_chromium_asan_rel_ng;luci.chromium.try:linux_chromium_tsan_rel_ng

Change-Id: I96e74da6d907659b939a0f229693bbd2a6d9140a
Reviewed-on: https://chromium-review.googlesource.com/1119098
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Peter Collingbourne <pcc@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578085}
10 files changed