Enable named mmap usage for Chromium
Enable named mmap usage for Chromium

Naming 'anonymous' mmap memory, which we use for Reactor's executable
memory, enables profilers to attribute JIT-compiled routine execution
to SwiftShader.

Also rename `swiftshader_reactor_private_config` to
`swiftshader_llvm_reactor_private_config` to clarify that it is only used
for building Reactor with the LLVM backend.

Bug: b/174801963
Change-Id: I4a6cb471b00f8403978870fd0be4608ee2798e54
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/52208
Presubmit-Ready: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>
Kokoro-Result: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Tested-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>
Reviewed-by: Antonio Maiorano <86d87a6550afb6b07035c9743fa181900589f7e0@google.com>

google/swiftshader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader