[sancov] add -sanitizer-coverage-drop-ctors (#137980)
[sancov] add -sanitizer-coverage-drop-ctors
Add a hidden flag to omit the @sancov.module_ctor* constructors.
When building kernel modules with sanitizer coverage enabled,
constructors may reference global symbols, creating unsupported
relocations. Because the kernel does not strictly need these
constructors in order for coverage to work, allow the user to omit
them.
Also apply clang-format to SanitizerCoverage.cpp.
Fixes PR132393.
