The pfx format has a huge performance loss with clang

• I can easily reproduce:

gcc from Ubuntu 24

$ john | head -1; sleep 3; john --test --format=pfx
John the Ripper 1.9.0-jumbo-1+bleeding-b3bd5ea707 2024-12-01 03:06:08 +0100 OMP [linux-gnu 64-bit x86_64 AVX2 AC]
Will run 8 OpenMP threads
Benchmarking: pfx, (.pfx, .p12) [PKCS#12 PBE (SHA1/SHA2) 256/256 AVX2 8x]... (8xOMP) DONE
Speed for cost 1 (iteration count) of 2048, cost 2 (mac-type [1:SHA1 224:SHA224 256:SHA256 384:SHA384 512:SHA512]) of 1
Raw:	26842 c/s real, 3696 c/s virtual

clang from Ubuntu 24.

$ $ run/john | head -1; sleep 3; run/john --test --format=pfx
John the Ripper 1.9.0-jumbo-1+bleeding-364b1ca435 2024-12-02 06:20:23 +0100 [linux-gnu 64-bit x86_64 AVX2 AC]
Benchmarking: pfx, (.pfx, .p12) [PKCS#12 PBE (SHA1/SHA2) 256/256 AVX2 8x2]... DONE
Speed for cost 1 (iteration count) of 2048, cost 2 (mac-type [1:SHA1 224:SHA224 256:SHA256 384:SHA384 512:SHA512]) of 1
Raw:	9792 c/s real, 9792 c/s virtual

$ run/john | head -1; sleep 3; run/john --test --format=pfx
John the Ripper 1.9.0-jumbo-1+bleeding-0251a0f0f8 2024-12-02 18:56:33 -0300 [linux-gnu 64-bit x86_64 AVX2 AC]
Benchmarking: pfx, (.pfx, .p12) [PKCS#12 PBE (SHA1/SHA2) 256/256 AVX2 8x]... DONE
Speed for cost 1 (iteration count) of 2048, cost 2 (mac-type [1:SHA1 224:SHA224 256:SHA256 384:SHA384 512:SHA512]) of 1
Raw:	11328 c/s real, 11328 c/s virtual

Start by reproducing the reported run/john --test --format=pfx benchmark with both GCC and Clang builds, using the commands and iteration costs shown in the issue. Trace the pfx format implementation and its compiler-sensitive path; done means the Clang benchmark no longer has the reported performance loss without regressing the GCC result.