Subzero: add subzeroEmitTextAsm flag
Subzero: add subzeroEmitTextAsm flag

If enabled, and ALLOW_DUMP = 1, emit() outputs text asm to stdout along
with liveness info. Useful for debugging register allocation.

Bug: b/144688789
Change-Id: I36137c439f6f2ca32af6f208146501b095ccfac4
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/38478
Tested-by: Antonio Maiorano <86d87a6550afb6b07035c9743fa181900589f7e0@google.com>
Reviewed-by: Ben Clayton <1f693eb7158dc33015048c09d6712f74dabddf79@google.com>
Kokoro-Presubmit: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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