Strip host-compiler -std flag from NVCC line.

Closes #8523.

mesonbuild/compilers/cuda.py

@@ -617,8 +617,19 @@ class CudaCompiler(Compiler):
         return opts
 
     def _to_host_compiler_options(self, options: 'KeyedOptionDictType') -> 'KeyedOptionDictType':
+        """
+        Convert an NVCC Option set to a host compiler's option set.
+        """
+
+        # We must strip the -std option from the host compiler option set, as NVCC has
+        # its own -std flag that may not agree with the host compiler's.
         overrides = {name: opt.value for name, opt in options.items()}
-        return OptionOverrideProxy(overrides, self.host_compiler.get_options())
+        overrides.pop(OptionKey('std', machine=self.for_machine,
+                                       lang=self.host_compiler.language), None)
+        host_options = self.host_compiler.get_options().copy()
+        if 'std' in host_options:
+            del host_options['std'] # type: ignore
+        return OptionOverrideProxy(overrides, host_options)
 
     def get_option_compile_args(self, options: 'KeyedOptionDictType') -> T.List[str]:
         args = self.get_ccbin_args(options)

test cases/cuda/16 multistd/main.cu

@@ -0,0 +1,20 @@
+#include <cuda_runtime.h>
+#include <iostream>
+
+auto cuda_devices(void) {
+    int result = 0;
+    cudaGetDeviceCount(&result);
+    return result;
+}
+
+
+int main(void) {
+    int n = cuda_devices();
+    if (n == 0) {
+        std::cout << "No Cuda hardware found. Exiting.\n";
+        return 0;
+    }
+
+    std::cout << "Found " << n << "Cuda devices.\n";
+    return 0;
+}

test cases/cuda/16 multistd/meson.build

@@ -0,0 +1,4 @@
+project('C++-CUDA multi-std', 'cpp', 'cuda', version : '1.0.0', default_options : ['cpp_std=c++17', 'cuda_std=c++14'])
+
+exe = executable('prog', 'main.cu')
+test('cudatest', exe)