GH-49981: [R][Packaging] Support building R package under r-universe/r-wasm

[amoeba]

Rationale for this change

Arrow C++ already supports Emscripten but the R package can't be built by either the r-wasm or r-universe projects in its current state. We just need to make the bundled build Emscripten aware we're in an Emscripten environment for this to work.

What changes are included in this PR?

• Adds Wasm detection to nixlibs.R
• Makes build_arrow_static.sh Emscripten-aware by adding support for being called with a wrapper program
• Adds a new crossbow job to test building the R package with r-wasm in the r-universe container

Are these changes tested?

Yes. The R package builds in a local docker r-wasm-based container as well as in Crossbow

Are there any user-facing changes?

No.

• GitHub Issue: [R][Packaging] Support building the R package under Emscripten #49981

[amoeba]

@github-actions crossbow submit test-r-r-universe-wasm

[github-actions]

Revision: 18fe759

Submitted crossbow builds: ursacomputing/crossbow @ actions-8ee2d3b170

Task	Status
test-r-r-universe-wasm

[amoeba]

@github-actions crossbow submit test-r-r-universe-wasm

[github-actions]

Revision: a2fa12a

Submitted crossbow builds: ursacomputing/crossbow @ actions-4178688350

Task	Status
test-r-r-universe-wasm

[amoeba]

@github-actions crossbow submit test-r-r-universe-wasm

[github-actions]

Revision: 5ee8457

Submitted crossbow builds: ursacomputing/crossbow @ actions-3963128ccf

Task	Status
test-r-r-universe-wasm

[amoeba]

@github-actions crossbow submit test-r-r-universe-wasm

[github-actions]

Revision: 5ee8457

Submitted crossbow builds: ursacomputing/crossbow @ actions-8c87567db5

Task	Status
test-r-r-universe-wasm

[amoeba]

@github-actions crossbow submit test-r-r-universe-wasm

[github-actions]

Revision: b37e9d0

Submitted crossbow builds: ursacomputing/crossbow @ actions-0aa60bce30

Task	Status
test-r-r-universe-wasm

[jonkeane]

Thanks for this! One comment about naming and then mostly questions for my understanding. This is exciting to see working!

[amoeba]

@github-actions crossbow submit test-r-wasm

[github-actions]

Revision: 7eb72ac

Submitted crossbow builds: ursacomputing/crossbow @ actions-df03aafab4

Task	Status
test-r-wasm

[amoeba]

Merged, thanks for the review.

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 3 benchmarking runs that have been run so far on merge-commit 876d50c.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 11 possible false positives for unstable benchmarks that are known to sometimes produce them.