Add two test recipes for cross compilation

One depending on the other.

tests/test-recipes/metadata/_cross_helloworld/.conda_build_config.yaml

@@ -0,0 +1,2 @@
+c_compiler: "gcc-osx-64"
+target_platform: "imx351uc"

tests/test-recipes/metadata/_cross_helloworld/meta.yaml

@@ -0,0 +1,20 @@
+package:
+  name: _cross_helloworld
+  version: 1.0
+
+source:
+  path: ./src
+
+requirements:
+  build:
+    - {{ compiler('c') }}
+    - xz
+  host:
+    - _cross_libgreeting
+
+build:
+  script:
+    - gcc helloworld.c -L${PREFIX}/lib -lgreeting -DGREETING_SUFFIX=$(xz --version | head -n 1) -o ${PREFIX}/bin/helloworld
+
+tests:
+  - strings ${PREFIX}/bin/helloworld | grep "XZ Utils"

tests/test-recipes/metadata/_cross_helloworld/src/helloworld.c

@@ -0,0 +1,14 @@
+#include <libgreeting.h>
+#include <stdio.h>
+
+int main(int argc, char * argv[])
+{
+    char * say_it = greeting(GREETING_SUFFIX);
+    if (say_it != NULL)
+    {
+        puts(say_it);
+        putc('\n');
+        return 0;
+    }
+    return 1;
+}

tests/test-recipes/metadata/_cross_libgreeting/.conda_build_config.yaml

@@ -0,0 +1,2 @@
+c-compiler: "gcc-osx-64"
+target_platform: "imx351uc"

tests/test-recipes/metadata/_cross_libgreeting/meta.yaml

@@ -0,0 +1,14 @@
+package:
+  name: _cross_libgreeting
+  version: 1.0
+
+requirements:
+  build:
+    - {{ compiler('c') }}
+
+build:
+  script:
+    - env
+    - gcc -o ${LDFLAGS} ${CFLAGS} libgreeting.o libgreeting.c
+    - ar cru ${PREFIX}/lib/libgreeting.a libgreeting.o
+    - cp libgreeting.h ${PREFIX}/include

tests/test-recipes/metadata/_cross_libgreeting/src/libgreeting.c

@@ -0,0 +1,14 @@
+#include <string.h>
+
+#define SALUTATION "Hello World! "
+
+char * greeting(char const * suffix)
+{
+    char * res = malloc(strlen(SALUTATION) + strlen(suffix) + 1);
+    if (res == NULL)
+        return NULL;
+    res[0] = '\0';
+    strcat(res, SALUTATION);
+    strcat(res, suffix);
+    return res;
+}

tests/test-recipes/metadata/_cross_libgreeting/src/libgreeting.h

@@ -0,0 +1,6 @@
+#ifndef LIBGREETING_H_INCLUDED
+#define LIBGREETING_H_INCLUDED
+
+char * greeting(char const * suffix);
+
+#endif /* LIBGREETING_H_INCLUDED */