GH-126910: Build/link the JIT shim in the Python interpreter

[diegorusso]

There are various reason why we want to do this but the main is to help simplifying #146071

The _PyJIT symbol (the shim) is now part of the python interpreter with its eh_frame and gdb can see it as normal symbol. There is no need to compile/emit code/eh_frame at runtime as this is done at build time.

• Issue: Supporting stack unwinding in the JIT compiler #126910

[diegorusso]

eh_frame of the shim is now present in the python binary

$ nm -an python | grep ' _PyJIT$'
000000000035e5b8 T _PyJIT

$ readelf --debug-dump=frames-interp python | grep -A4 -B1 '35e5b8'
  0xffffffffffdbbf88 (offset: 0x35d568) -> 0x66f08 fde=[ 564a0]
  0xffffffffffdbcfd8 (offset: 0x35e5b8) -> 0x66f4c fde=[ 564e4]
  0xffffffffffdbd060 (offset: 0x35e640) -> 0x66fc0 fde=[ 56558]
  0xffffffffffdbd1c4 (offset: 0x35e7a4) -> 0x6701c fde=[ 565b4]
  0xffffffffffdbd2e0 (offset: 0x35e8c0) -> 0x67050 fde=[ 565e8]
  0xffffffffffdbd3cc (offset: 0x35e9ac) -> 0x67088 fde=[ 56620]
--

000564e4 0000000000000070 00000018 FDE cie=000564d0 pc=000000000035e5b8..000000000035e634
   LOC           CFA      x19   x20   x21   x22   x23   x24   x25   x26   x27   x28   x29   ra    v8    v9    v10   v11   v12   v13   v14   v15
000000000035e5b8 sp+0     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u
000000000035e5bc sp+160   u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u
000000000035e5e4 x29+96   c-8   c-16  c-24  c-32  c-40  c-48  c-56  c-64  c-72  c-80  c-96  c-88  c-104 c-112 c-120 c-128 c-136 c-144 c-152 c-160
000000000035e608 sp+160   c-8   c-16  c-24  c-32  c-40  c-48  c-56  c-64  c-72  c-80  c-96  c-88  c-104 c-112 c-120 c-128 c-136 c-144 c-152 c-160
000000000035e630 sp+0     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u     u

[markshannon]

Looks good.