fix(amd64): re-add signal support

[LouisBrunner]

Split from #126

Changes:

• Re-add the amd64 signals blocking during syscalls
• Clean up the arm64 syscall assembly and use __NR___pthread_sigmask as suggested for amd64

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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