Compilation fails when PVQ program references `polkadot-sdk` dependency

[mise42]

Some data structures' definitions utilized in PVQ programs may originate from external dependencies. For instance, AssetId can be an XCM Location, whose definition resides in the external dependency polkadot-sdk/staging-xcm. However, compilation fails when specifying the build target ../vendor/polkavm/crates/polkavm-linker/riscv32emac-unknown-none-polkavm.json.

 cargo:warning=depend/secp256k1/contrib/lax_der_parsing.c:7:10: fatal error: 'string.h' file not found
  cargo:warning=    7 | #include <string.h>
  cargo:warning=      |          ^~~~~~~~~~
  cargo:warning=1 error generated.
  cargo:warning=error: unable to create target: 'No available targets are compatible with triple "riscv32-unknown-none-polkavm"'
  cargo:warning=1 error generated.

Current workaround: Introducing an opaque data structure for direct args passing.
Future work: Investigate the root cause of the failure, as the polkadot-sdk claims it can be compiled to the riscv architecture, according to paritytech/polkadot-sdk#6704.