[BUG] `build.rs` unnecessarily uses `mut` where the variable is actually immutable

[Abhishek Kumar]

CCExtractor version: 0.94

Using mut where the variable is actually never mutated is considered bad practice. Running the ./build scripts for example, output the following warnings:

Building rust files...
-g -std=gnu99 -Wno-write-strings -Wno-pointer-sign -DGPAC_CONFIG_LINUX -D_FILE_OFFSET_BITS=64 -DVERSION_FILE_PRESENT -DENABLE_OCR -DFT2_BUILD_LIBRARY -DGPAC_DISABLE_VTT -DGPAC_DISABLE_OD_DUMP -DGPAC_DISABLE_REMOTERY -DNO_GZIP -DGPAC_HAVE_CONFIG_H -DGPAC_64_BITS
warning: variable does not need to be mutable
 --> build.rs:5:9
  |
5 |     let mut allowlist_functions = vec![
  |         ----^^^^^^^^^^^^^^^^^^^
  |         |
  |         help: remove this `mut`
  |
  = note: `#[warn(unused_mut)]` on by default

warning: variable does not need to be mutable
  --> build.rs:21:9
   |
21 |     let mut allowlist_types = vec![
   |         ----^^^^^^^^^^^^^^^
   |         |
   |         help: remove this `mut`

warning: `ccx_rust` (build script) generated 2 warnings

[Abhishek Kumar]

PR #1470 should fix this.

[Abhishek Kumar]

Update: The two variables actually need to be borrowed as mutables.