jit-diff --pmi --altjit doesn't generate SIMD code

Looking at pmi of System.Private.Corelib with an altjit, I see disassembly like:
```asm
; Assembly listing for method Simd:Abs(struct):struct
; Emitting BLENDED_CODE for X64 CPU with AVX
; optimized code
; rsp based frame
; partially interruptible
; Final local variable assignments
;
;* V00 arg0 [V00 ] ( 0, 0 ) struct ( 8) zero-ref
;# V01 OutArgs [V01 ] ( 1, 1 ) lclBlk ( 0) [rsp+0x00]
; V02 tmp1 [V02,T00] ( 3, 0 ) ref -> rbx class-hnd exact
;* V03 tmp2 [V03 ] ( 0, 0 ) long -> zero-ref V00._00(offs=0x00) P-INDEP
;
; Lcl frame size = 0
G_M1197_IG01:
push rbx
G_M1197_IG02:
mov rdi, 0xD1FFAB1E
call CORINFO_HELP_NEWSFAST
mov rbx, rax
mov rdi, rbx
call PlatformNotSupportedException:.ctor():this
mov rdi, rbx
call CORINFO_HELP_THROW
int3
; Total bytes of code 36, prolog size 1 for method Simd:Abs(struct):struct
```
We may need some extra setup to see codegen for SIMD methods here.