SIGTRAP when EbSvtAv1EncConfiguration::avif=0

[y-guyon]

libavif's avifsvttest is failing at head (flaky) with the following message:

[ RUN      ] All/SvtAv1Test.EncodeDecodeStillImage/1
Svt[info]: -------------------------------------------
Svt[info]: SVT [version]:	SVT-AV1 Encoder Lib v3.0.0
Svt[info]: SVT [build]  :	Apple LLVM 15.0.0 (clang-1500.3.9.4)	 64 bit
Svt[info]: LIB Build date: Feb 26 2025 10:40:51
Svt[info]: -------------------------------------------
Svt[info]: Level of Parallelism: 1
Svt[info]: Number of PPCS 74
Svt[info]: [asm level on system : up to neon_dotprod]
Svt[info]: [asm level selected : up to neon_dotprod]
Svt[info]: -------------------------------------------
Svt[info]: SVT [config]: main profile	tier (auto)	level (auto)
Svt[info]: SVT [config]: width / height / fps numerator / fps denominator 		: 64 / 64 / 60000 / 1000
Svt[info]: SVT [config]: bit-depth / color format 					: 8 / YUV420
Svt[info]: SVT [config]: preset / tune / pred struct 					: 8 / PSNR / random access
Svt[info]: SVT [config]: gop size / mini-gop size / key-frame type 			: 321 / 32 / key frame
Svt[info]: SVT [config]: BRC mode / rate factor 					: CRF / 63 
Svt[info]: SVT [config]: AQ mode / variance boost 					: 2 / 0
Svt[info]: SVT [config]: sharpness / luminance-based QP bias 			: 0 / 0
Svt[info]: Svt[info]: -------------------------------------------
Error: Svt[error]: A single picture was detected. Consider using --avif 1 for improved efficiency and reduced memory usage.
[       OK ] All/SvtAv1Test.EncodeDecodeStillImage/1 (5 ms)

While the GoogleTest unit passes, ctest reports a failure:

The following tests FAILED:
	 46 - avifsvttest (SIGTRAP)
Error: Process completed with exit code 8.

libavif cannot use EbSvtAv1EncConfiguration::avif because of #2245.

See https://gitlab.com/AOMediaCodec/SVT-AV1/-/issues/2251.