Missing libm linkage causes undefined symbol errors in Cython extensions

When building fontTools from source on Linux (aarch64), some Cython extension modules fail to load at runtime due to missing linkage against libm.

The affected extensions use math functions provided by libm (such as sqrt, pow, fabs, etc.), but do not explicitly link against it. As a result, importing the modules fails with undefined symbol errors.

Affected modules:
- fontTools.cu2qu.cu2qu
- fontTools.qu2cu.qu2cu
- fontTools.misc.bezierTools
- fontTools.pens.momentsPen

Example error output:
```bash
[./lib/python3.12/site-packages/fontTools/cu2qu/cu2qu.cpython-312-aarch64-linux-gnu.so]:
    linux-vdso.so.1 (0x0000ffff907d7000)
    libc.so.6 => /lib64/libc.so.6 (0x0000ffff90570000)
    /lib/ld-linux-aarch64.so.1 (0x0000ffff9078a000)
undefined symbol: sqrt	(./lib/python3.12/site-packages/fontTools/cu2qu/cu2qu.cpython-312-aarch64-linux-gnu.so)
undefined symbol: pow	(./lib/python3.12/site-packages/fontTools/cu2qu/cu2qu.cpython-312-aarch64-linux-gnu.so)
```

Workaround is to manually patch setup.py to explicitly link against libm:
```bash
sed -i \
  -e '/Extension("fontTools\.cu2qu\.cu2qu",.*\["Lib\/fontTools\/cu2qu\/cu2qu\.py"\]/ s/\])/], libraries=["m"])/' \
  -e '/Extension("fontTools\.qu2cu\.qu2cu",.*\["Lib\/fontTools\/qu2cu\/qu2qu\.py"\]/ s/\])/], libraries=["m"])/' \
  -e '/Extension("fontTools\.misc\.bezierTools",.*\["Lib\/fontTools\/misc\/bezierTools\.py"\]/ s/\])/], libraries=["m"])/' \
  -e '/Extension("fontTools\.pens\.momentsPen",.*\["Lib\/fontTools\/pens\/momentsPen\.py"\]/ s/\])/], libraries=["m"])/' \
  "./setup.py"
```

Environment:

fontTools version: 4.61.1
OS: Amazon Linux 2023 (aarch64)
Python: 3.12.x
Compiler: Clang 20 (git)

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