Change to use arena allocation for function-local data in parser.

src/IceCfg.cpp

Index: src/IceCfg.cpp
diff --git a/src/IceCfg.cpp b/src/IceCfg.cpp
index 4288f6d16b32acc8e358a28fd8374d2e0df57a1c..218ecd9017197485c2e0a2401daf0700b655e268 100644
--- a/src/IceCfg.cpp
+++ b/src/IceCfg.cpp
@@ -43,8 +43,6 @@ Cfg::Cfg(GlobalContext *Ctx, uint32_t SequenceNumber)
       VMetadata(new VariablesMetadata(this)),
       TargetAssembler(TargetLowering::createAssembler(
           Ctx->getFlags().getTargetArch(), this)) {
-  assert(!Ctx->isIRGenerationDisabled() &&
-         "Attempt to build cfg when IR generation disabled");
 }
 
 Cfg::~Cfg() { assert(ICE_TLS_GET_FIELD(CurrentCfg) == nullptr); }