Add swiftshader_optimized_debug_build gn arg
Add swiftshader_optimized_debug_build gn arg

True by default, allows forcing non-optimized builds of SwiftShader in
debug builds.

Bug: b/140251624
Change-Id: I51bb93b53ead5936b47894ebabbd73b36c05cae0
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/36470
Tested-by: Antonio Maiorano <86d87a6550afb6b07035c9743fa181900589f7e0@google.com>
Reviewed-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>

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