Makefile.system: -lm is necessary on power as well

[pkubaj]

No description provided.

[codspeed-hq]

Merging this PR will improve performance by 17.44%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

#### 🎉 Hooray! `pytest-codspeed` just leveled up to 5.0.1!

A heads-up, this is a breaking change and it might affect your current performance baseline a bit. But here's the exciting part - it's packed with new, cool features and promises improved result stability 🥳!
Curious about what's new? Visit our releases page to delve into all the awesome details about this new version.

⚡ 15 improved benchmarks
✅ 47 untouched benchmarks

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	test_daxpy[100-c]	25.3 µs	21.5 µs	+17.82%
⚡	test_daxpy[100-d]	24.3 µs	20.5 µs	+18.48%
⚡	test_daxpy[100-s]	24.2 µs	20.4 µs	+18.91%
⚡	test_daxpy[100-z]	26 µs	22.2 µs	+17.26%
⚡	test_daxpy[1000-c]	32.9 µs	29.1 µs	+13.19%
⚡	test_daxpy[1000-d]	32.6 µs	28.3 µs	+15.41%
⚡	test_daxpy[1000-s]	27.7 µs	23.8 µs	+16.35%
⚡	test_nrm2[100-d]	37.7 µs	25.7 µs	+46.87%
⚡	test_nrm2[100-dz]	28.9 µs	25.4 µs	+13.95%
⚡	test_daxpy[1000-z]	40.7 µs	37 µs	+10.21%
⚡	test_nrm2[1000-d]	30.6 µs	26.9 µs	+13.93%
⚡	test_nrm2[1000-dz]	35.5 µs	31.8 µs	+11.73%
⚡	test_dgbmv[1-100-s]	37.4 µs	34 µs	+10.17%
⚡	test_dot[1000]	28.4 µs	24.5 µs	+15.98%
⚡	test_dot[100]	22.5 µs	17.9 µs	+25.59%

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing pkubaj:patch-4 (9cb7d39) with develop (3da0ff7)}