Snippy ignores the function-number option when call-graph is specified

[ruslan-sc]

Currently, snippy behaves normally when both `function-number' and 'call-graph' are specified in the layout, and it simply generates the number of functions according to the 'call-graph'. 'function-number' is completely ignored in this case. I’m sure it should be something like an error

Snippy command line:
./llvm-snippy layout.yaml

layout.yaml:

options:
  mtriple: riscv64-unknown-elf
  mattr: +m
  model-plugin: None
  function-number: 37
  num-instrs: 100
  dump-mf: true

sections:
  - name:      text
    VMA:       0x210000
    SIZE:      0x100000
    LMA:       0x210000
    ACCESS:    rx
  - name:      data
    VMA:       0x100000
    SIZE:      0x50000
    LMA:       0x100000
    ACCESS:    rw
  - name:      rodata
    VMA:       0x310000
    SIZE:      0x50000
    LMA:       0x360000
    ACCESS:    r

histogram:
    - [ADD, 1.0]
    - [ADDI, 1.0]
    - [SUB, 1.0]
    - [MUL, 1.0]

call-graph:
  entry-point: SnippyFunction
  function-list:
    - name: SnippyFunction
      callees:
        - fun1
        - fun2
        - fun3
    - name: fun1
      callees:
        - fun2
    - name: fun2
      callees:
        - fun3
    - name: fun3
      external: true

[MaxGud10]

Hi! I’ve opened PR #420 with a fix for this issue.