aws-sdk-cpp: fix cross compilation

[erictapen]

Motivation for this change

Fix cross compilation of nix: nix build nixpkgs.pkgsCross.aarch64-multiplatform.nix

...
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Updating version info to 1.7.90
-- Custom memory management disabled
-- Performing Test CURL_HAS_H2
CMake Error: TRY_RUN() invoked in cross-compiling mode, please set the following cache variables appropriately:
   CURL_HAS_H2_EXITCODE (advanced)
   CURL_HAS_H2_EXITCODE__TRYRUN_OUTPUT (advanced)
For details see /build/source/build/TryRunResults.cmake
-- Performing Test CURL_HAS_H2 - Failed
-- Configuring incomplete, errors occurred!
See also "/build/source/build/CMakeFiles/CMakeOutput.log".
See also "/build/source/build/CMakeFiles/CMakeError.log".
builder for '/nix/store/wagq7k2fbgkl32alzfh5f4ysgpvsi4jw-aws-sdk-cpp-1.7.90-aarch64-unknown-linux-gnu.drv' failed with exit code 1
cannot build derivation '/nix/store/lkbs04l8a4489pykvfrjj0r4vc8y2k2i-nix-2.2.2-aarch64-unknown-linux-gnu.drv': 1 dependencies couldn't be built
error: build of '/nix/store/lkbs04l8a4489pykvfrjj0r4vc8y2k2i-nix-2.2.2-aarch64-unknown-linux-gnu.drv' failed

I think the problem was introduced in aws/aws-sdk-cpp@f024f1d.

Things done

Provided the expected result of a CMake try_run call. I'm really unsure about wether this is supposed to be 0 or 1. The exit code of the test should be 0 and the docs say that the variable should be set to the exit code, but it might be better if someone double checked wether this really translates to -DCURL_HAS_H2=0.

I did not run the build result, as I have no access to aarch64 hardware atm.

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nix-review --run "nix-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Assured whether relevant documentation is up to date
• Fits CONTRIBUTING.md.

---

[erictapen]

@GrahamcOfBorg build pkgsCross.aarch64-multiplatform.nix

[erictapen]

@GrahamcOfBorg build aws-sdk-cpp

[matthewbauer]

@erictapen looks good to me if pkgsCross.aarch64-multiplatform.nix builds. Can't build it right now though

[lukateras]

Thank you!