core: Arch: add method to map to Go arch (MR 2474)

Map architectures to the strings used for GOARCH for cross compiling Go
applications.

Signed-off-by: Caleb Connolly <caleb@postmarketos.org>

pmb/core/arch.py

@@ -182,6 +182,21 @@ class Arch(enum.Enum):
                     f"Can not map Alpine architecture '{self}' to the right hostspec value"
                 )
 
+    def go(self) -> str:
+        match self:
+            case Arch.armhf | Arch.armv7:
+                return "arm"
+            case Arch.aarch64:
+                return "arm64"
+            case Arch.riscv64 | Arch.ppc64le:
+                return str(self)
+            case Arch.x86:
+                return "386"
+            case Arch.x86_64:
+                return "amd64"
+            case _:
+                raise ValueError(f"Can not map architecture '{self}' to Go arch")
+
     def cpu_emulation_required(self) -> bool:
         # Obvious case: host arch is target arch
         if self == Arch.native():

test/core/test_arch.py

@@ -49,6 +49,17 @@ def test_valid_arches():
     assert Arch.ppc64.qemu() == "ppc64"
     assert Arch.ppc64le.qemu() == "ppc64"
 
+    # Go arch
+    assert Arch.armhf.go() == "arm"
+    assert Arch.armv7.go() == "arm"
+    assert Arch.aarch64.go() == "arm64"
+    assert Arch.riscv64.go() == "riscv64"
+    assert Arch.ppc64le.go() == "ppc64le"
+    assert Arch.x86_64.go() == "amd64"
+    with pytest.raises(ValueError) as excinfo:
+        Arch.mips64.go()
+    assert "Can not map architecture 'mips64' to Go arch" in str(excinfo.value)
+
     # Check that Arch.cpu_emulation_required() works
     assert Arch.native() == Arch.x86_64 or Arch.x86_64.cpu_emulation_required()
     assert Arch.native() == Arch.aarch64 or Arch.aarch64.cpu_emulation_required()