Allow specifying a C++ std for building Rust

Signed-off-by: Scott Wilson <scott@propersquid.com>

Author: scott-wilson

.github/workflows/build-steps.yml

@@ -157,6 +157,8 @@ jobs:
       - name: Rust Test
         if: inputs.rust == '1'
         shell: bash
+        env:
+          OIIO_CXX_STANDARD: c++${{inputs.cxx_std}}
         run: src/build-scripts/ci-rust-test.bash
       - name: Code coverage
         if: inputs.coverage == '1'

src/build-scripts/ci-rust-test.bash

@@ -14,6 +14,8 @@ fi
 export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$OpenImageIO_ROOT/lib
 export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:$OpenImageIO_ROOT/lib/pkgconfig
 
+echo "Using C++ STD ${OIIO_CXX_STANDARD}"
+
 echo "Running Rust oiio-sys tests"
 
 pushd src/rust/oiio-sys

src/rust/oiio-sys/build.rs

@@ -19,9 +19,11 @@ fn main() -> Result<()> {
     let pkgconfig = pkg_config::probe_library("OpenImageIO")?;
     include_paths.extend(pkgconfig.include_paths);
 
+    let std_version = std::env::var("OIIO_CXX_STANDARD").unwrap_or("c++17".to_string());
+
     cxx_build::bridges(NAMES.iter().map(|s| format!("src/{}.rs", s)))
         .files(NAMES.iter().map(|s| format!("src/{}.cpp", s)))
-        .std("c++17")
+        .std(&std_version)
         .includes(&include_paths)
         .compile("oiio-sys");