Exclude PCG on MacOS PowerPC

[rstub]

fixes #88

[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if ba5be53 is merged into main:

• ✔️rexp_test: 81.8ms -> 81.5ms [-2.8%, +2.01%]
• ✔️rnorm_test: 105ms -> 105ms [-1.64%, +0.88%]
• ✔️runif_test: 66.2ms -> 67.1ms [-1.56%, +4.4%]
  Further explanation regarding interpretation and methodology can be found in the documentation.

[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if ac8ebb3 is merged into main:

• ✔️rexp_test: 82.8ms -> 81.1ms [-5.85%, +1.8%]
• ✔️rnorm_test: 105ms -> 105ms [-1.56%, +1.32%]
• ✔️runif_test: 66.7ms -> 66.3ms [-2.31%, +1.16%]
  Further explanation regarding interpretation and methodology can be found in the documentation.

[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if d5c4912 is merged into main:

• ✔️rexp_test: 81.6ms -> 82.2ms [-3.88%, +5.32%]
• ✔️rnorm_test: 106ms -> 106ms [-1.99%, +2.36%]
• ✔️runif_test: 68.2ms -> 67.7ms [-4.26%, +2.79%]
  Further explanation regarding interpretation and methodology can be found in the documentation.