Add introspection for readelf

[am11]

Just like CMAKE_NM, which is used by verify-entrypoints.sh, introspect CMAKE_READELF for genmoduleindex.sh.

I saw some warnings in riscv64 logs in @clamp03's PR #85289. Those warnings are reported by binutils readelf, which doesn't seem to handle DWARF 5 very well:

2023-04-25T06:24:05.8822869Z [ 96%] Generating coreclr module index file -> /__w/1/s/artifacts/obj/coreclr/linux.riscv64.Checked/debug/runtimeinfo/runtimemoduleindex.h
2023-04-25T06:24:05.9454927Z readelf: Warning: Unrecognized form: 0x23
2023-04-25T06:24:05.9574180Z readelf: Warning: Unrecognized form: 0x22
2023-04-25T06:24:05.9574395Z readelf: Warning: Unrecognized form: 0x22
...
2023-04-25T06:24:05.9575038Z readelf: Warning: Bogus end-of-siblings marker detected at offset 5131 in .debug_info section
2023-04-25T06:24:05.9575305Z readelf: Warning: Unrecognized form: 0x22
2023-04-25T06:24:05.9575728Z readelf: Warning: Bogus end-of-siblings marker detected at offset 5147 in .debug_info section
2023-04-25T06:24:05.9576205Z readelf: Warning: Bogus end-of-siblings marker detected at offset 5156 in .debug_info section
2023-04-25T06:24:05.9577004Z readelf: Warning: Further warnings about bogus end-of-sibling markers suppressed
2023-04-25T06:24:05.9577299Z readelf: Warning: Unrecognized form: 0x23
2023-04-25T06:24:05.9577497Z readelf: Warning: Unrecognized form: 0x22
2023-04-25T06:24:05.9577714Z readelf: Warning: Unrecognized form: 0x22

With this change, the script uses llvm-readelf-15 in that container (matching the exact toolchain in use) and reports no warning.

Also removed the usage of eval in the script while I was at it.

[ghost]

Tagging subscribers to this area: @tommcdon
See info in area-owners.md if you want to be subscribed.

Issue Details

---

null

Author:	am11
Assignees:	-
Labels:	area-Diagnostics-coreclr, community-contribution
Milestone:	-

[ghost]

Tagging subscribers to this area: @hoyosjs
See info in area-owners.md if you want to be subscribed.

Issue Details

---

null

Author:	am11
Assignees:	-
Labels:	area-Infrastructure-coreclr, community-contribution
Milestone:	-

[clamp03]

Thank you. You fixed errors in other archs like the one below

2023-04-25T06:26:04.3961679Z [ 95%] Built target coreclr
2023-04-25T06:26:04.4105174Z [ 95%] Generating coreclr module index file -> /__w/1/s/artifacts/obj/coreclr/linux.arm64.Checked/debug/runtimeinfo/runtimemoduleindex.h
2023-04-25T06:26:04.4194263Z /__w/1/s/eng/native/genmoduleindex.sh: line 40: readelf: command not found
2023-04-25T06:26:04.4259540Z [ 95%] Generating mscordaccore module index file -> /__w/1/s/artifacts/obj/coreclr/linux.arm64.Checked/debug/runtimeinfo/dacmoduleindex.h
2023-04-25T06:26:04.4344655Z /__w/1/s/eng/native/genmoduleindex.sh: line 40: readelf: command not found
2023-04-25T06:26:04.4407639Z [ 96%] Generating mscordbi module index file -> /__w/1/s/artifacts/obj/coreclr/linux.arm64.Checked/debug/runtimeinfo/dbimoduleindex.h
2023-04-25T06:26:04.4500891Z /__w/1/s/eng/native/genmoduleindex.sh: line 40: readelf: command not found

2023-04-25T06:24:12.1859277Z [ 94%] Built target coreclr
2023-04-25T06:24:12.1945446Z [ 94%] Generating coreclr module index file -> /__w/1/s/artifacts/obj/coreclr/linux.arm.Checked/debug/runtimeinfo/runtimemoduleindex.h
2023-04-25T06:24:12.2052980Z /__w/1/s/eng/native/genmoduleindex.sh: line 40: readelf: command not found
2023-04-25T06:24:12.2127116Z [ 94%] Generating mscordaccore module index file -> /__w/1/s/artifacts/obj/coreclr/linux.arm.Checked/debug/runtimeinfo/dacmoduleindex.h
2023-04-25T06:24:12.2236387Z /__w/1/s/eng/native/genmoduleindex.sh: line 40: readelf: command not found
2023-04-25T06:24:12.2305188Z [ 94%] Generating mscordbi module index file -> /__w/1/s/artifacts/obj/coreclr/linux.arm.Checked/debug/runtimeinfo/dbimoduleindex.h
2023-04-25T06:24:12.2408735Z /__w/1/s/eng/native/genmoduleindex.sh: line 40: readelf: command not found

[janvorli]

LGTM, thank you!

[am11]

Mono failures are unrelated / known failures according to build analysis.
This cleans up 1105 warnings in riscv64 leg.

[hoyosjs]

All issues are known