fix(cmake): rework ucontext_t introspection

[sergiud]

Fixes #953

@cieplik Does this work for you?

[cieplik]

Fixes #953

@cieplik Does this work for you?

@sergiud, thank you for the PR, I'll check it early next week and will let you know.

[cieplik]

Fixes #953
@cieplik Does this work for you?

@sergiud, thank you for the PR, I'll check it early next week and will let you know.

@sergiud, that works for me on aarch64 Linux:

-- Performing Test HAVE_PC_FROM_UCONTEXT_uc_mcontext_gregs_REG_RIP
-- Performing Test HAVE_PC_FROM_UCONTEXT_uc_mcontext_gregs_REG_RIP - Failed
-- Performing Test HAVE_PC_FROM_UCONTEXT_uc_mcontext_sc_ip
-- Performing Test HAVE_PC_FROM_UCONTEXT_uc_mcontext_sc_ip - Failed
-- Performing Test HAVE_PC_FROM_UCONTEXT_uc_mcontext_pc
-- Performing Test HAVE_PC_FROM_UCONTEXT_uc_mcontext_pc - Success

$ cat config.h | grep PC
/* How to access the PC from a struct ucontext */
#define PC_FROM_UCONTEXT uc_mcontext.pc

Thank you!

[sergiud]

@cieplik Thanks for validating the fix!