break the triples logic into its own class

This is so we can use the Rust triples in Cargo builds and other places
in addition to the Rust build.

classes/rust-triples.bbclass

@@ -0,0 +1,31 @@
+# Responseible for taking Yocto triples and converting it to Rust triples
+
+def rust_base_triple(d, thing):
+    '''
+    Mangle bitbake's *_SYS into something that rust might support (see
+    rust/mk/cfg/* for a list)
+
+    Note that os is assumed to be some linux form
+    '''
+
+    arch = d.getVar('{}_ARCH'.format(thing), True)
+    vendor = d.getVar('{}_VENDOR'.format(thing), True)
+    os = d.getVar('{}_OS'.format(thing), True)
+
+    vendor = "-unknown"
+
+    if arch.startswith("arm"):
+        if os.endswith("gnueabi"):
+            os += bb.utils.contains('TUNE_FEATURES', 'callconvention-hard', 'hf', '', d)
+    elif arch.startswith("aarch64"):
+        os = "linux-gnu"
+    elif arch.startswith("x86_64"):
+        os = "linux-gnu"
+    elif arch.startswith("i586"):
+        arch = "i686"
+        os = "linux-gnu"
+    return arch + vendor + '-' + os
+
+RUST_BUILD_SYS = "${@rust_base_triple(d, 'BUILD')}"
+RUST_HOST_SYS = "${@rust_base_triple(d, 'HOST')}"
+RUST_TARGET_SYS = "${@rust_base_triple(d, 'TARGET')}"

classes/rust.bbclass

@@ -1,4 +1,5 @@
 inherit rust-vars
+inherit rust-triples
 
 RUSTC = "rustc"
 
@@ -17,36 +18,6 @@ def rust_base_dep(d):
 
 DEPENDS_append = " ${@rust_base_dep(d)} patchelf-native"
 
-def rust_base_triple(d, thing):
-    '''
-    Mangle bitbake's *_SYS into something that rust might support (see
-    rust/mk/cfg/* for a list)
-
-    Note that os is assumed to be some linux form
-    '''
-
-    arch = d.getVar('{}_ARCH'.format(thing), True)
-    vendor = d.getVar('{}_VENDOR'.format(thing), True)
-    os = d.getVar('{}_OS'.format(thing), True)
-
-    vendor = "-unknown"
-
-    if arch.startswith("arm"):
-        if os.endswith("gnueabi"):
-            os += bb.utils.contains('TUNE_FEATURES', 'callconvention-hard', 'hf', '', d)
-    elif arch.startswith("aarch64"):
-        os = "linux-gnu"
-    elif arch.startswith("x86_64"):
-        os = "linux-gnu"
-    elif arch.startswith("i586"):
-        arch = "i686"
-        os = "linux-gnu"
-    return arch + vendor + '-' + os
-
-RUST_BUILD_SYS = "${@rust_base_triple(d, 'BUILD')}"
-RUST_HOST_SYS = "${@rust_base_triple(d, 'HOST')}"
-RUST_TARGET_SYS = "${@rust_base_triple(d, 'TARGET')}"
-
 # BUILD_LDFLAGS
 # 	${STAGING_LIBDIR_NATIVE}
 # 	${STAGING_BASE_LIBDIR_NATIVE}