feat: add musllinux armv7l (#2017)

* feature: add musllinux armv7l

* fix: local armv7l images

* fix python 3.8 tests

* address review comments

---------

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>

cibuildwheel/oci_container.py

@@ -38,6 +38,7 @@ ContainerEngineName = Literal["docker", "podman"]
 class OCIPlatform(Enum):
     i386 = "linux/386"
     AMD64 = "linux/amd64"
+    ARMV7 = "linux/arm/v7"
     ARM64 = "linux/arm64"
     PPC64LE = "linux/ppc64le"
     S390X = "linux/s390x"
@@ -208,7 +209,11 @@ class OCIContainer:
                 "inspect",
                 self.image,
                 "--format",
-                "{{.Os}}/{{.Architecture}}",
+                (
+                    "{{.Os}}/{{.Architecture}}/{{.Variant}}"
+                    if len(oci_platform.value.split("/")) == 3
+                    else "{{.Os}}/{{.Architecture}}"
+                ),
                 capture_stdout=True,
             ).strip()
             if image_platform == oci_platform.value:
@@ -235,7 +240,7 @@ class OCIContainer:
         platform_args = self._get_platform_args()
 
         simulate_32_bit = False
-        if self.oci_platform == OCIPlatform.i386:
+        if self.oci_platform in {OCIPlatform.i386, OCIPlatform.ARMV7}:
             # If the architecture running the image is already the right one
             # or the image entrypoint takes care of enforcing this, then we don't need to
             # simulate this
@@ -246,13 +251,14 @@ class OCIContainer:
                     *run_cmd, *platform_args, self.image, *ctr_cmd, capture_stdout=True
                 ).strip()
             except subprocess.CalledProcessError:
-                # The image might have been built with amd64 architecture
-                # Let's try that
-                platform_args = self._get_platform_args(oci_platform=OCIPlatform.AMD64)
-                container_machine = call(
-                    *run_cmd, *platform_args, self.image, *ctr_cmd, capture_stdout=True
-                ).strip()
-            simulate_32_bit = container_machine != "i686"
+                if self.oci_platform == OCIPlatform.i386:
+                    # The image might have been built with amd64 architecture
+                    # Let's try that
+                    platform_args = self._get_platform_args(oci_platform=OCIPlatform.AMD64)
+                    container_machine = call(
+                        *run_cmd, *platform_args, self.image, *ctr_cmd, capture_stdout=True
+                    ).strip()
+            simulate_32_bit = container_machine not in {"i686", "armv7l", "armv8l"}
 
         shell_args = ["linux32", "/bin/bash"] if simulate_32_bit else ["/bin/bash"]