Support sandboxing inputs in RuleBuilder

When RuleBuilder.SandboxInputs() is called configure sbox to copy
all the input files into the sandbox directory and then change the
working directory there when running the command.

Copying input files into the sandbox directory gets tricky when
the input file is the output file from another rule, and could
be at an arbitrary, possibly absolute path based on the value
of OUT_DIR.  They will need to be copied to a directory in the
sandbox using the path relative to OUT_DIR.

RSP files need special handling, they need to both be copied into
the sandbox as an input, rewritten to contain paths as seen in the
sandbox, and references to them on the command line need to use
sandbox paths.

Bug: 182612695
Test: rule_builder_test.go
Change-Id: Ic0db961961b186e4ed9b76246881e3f04971825c