Introduce a 'baseline' variant for the compiler.

Implemented as a stripped down version of the optimizing compiler,
not running any optimization.

Adjust code to still work with expectations in code generators.

bug: 111397239

Test: test.py --baseline
Change-Id: I4328283825f9a890616e7496ed4c1e77d6bcc5dd
diff --git a/compiler/driver/compiler_options.cc b/compiler/driver/compiler_options.cc
index 8cc6cf1..3ab9afc 100644
--- a/compiler/driver/compiler_options.cc
+++ b/compiler/driver/compiler_options.cc
@@ -47,6 +47,7 @@
       boot_image_(false),
       core_image_(false),
       app_image_(false),
+      baseline_(false),
       debuggable_(false),
       generate_debug_info_(kDefaultGenerateDebugInfo),
       generate_mini_debug_info_(kDefaultGenerateMiniDebugInfo),