Use ; as classpath separator on Windows

Speculative fix for this error seen in CI:
```
Exception in thread "main" java.nio.file.InvalidPathException: Illegal char <:> at index 77: bazel-out/x64_windows-fastbuild/bin/src/main/protobuf/libdeps_proto-speed.jar:bazel-out/x64_windows-fastbuild/bin/external/com_google_protobuf/java/core/libcore.jar:bazel-out/x64_windows-fastbuild/bin/external/com_google_protobuf/java/core/liblite_runtime_only.jar:bazel-out/x64_windows-fastbuild/bin/external/maven/com/google/guava/guava/31.1-jre/guava-31.1-jre.jar:bazel-out/x64_windows-fastbuild/bin/external/maven/com/google/guava/failureaccess/1.0.1/failureaccess-1.0.1.jar:bazel-out/x64_windows-fastbuild/bin/external/maven/com/google/errorprone/error_prone_annotations/2.20.0/processed_error_prone_annotations-2.20.0.jar:bazel-out/x64_windows-fastbuild/bin/external/maven/com/google/errorprone/error_prone_type_annotations/2.20.0/processed_error_prone_type_annotations-2.20.0.jar:bazel-out/x64_windows-fastbuild/bin/external/maven/com/github/stephenc/jcip/jcip-annotations/1.0-1/processed_jcip-annotations-1.0-1.jar:bazel-out/x64_windows-fastbuild/bin/external/maven/com/google/code/findbugs/jsr305/3.0.2/processed_jsr305-3.0.2.jar:third_party/turbine/turbine_direct.jar
	at java.base@20.0.2/sun.nio.fs.WindowsPathParser.normalize(WindowsPathParser.java:182)
	at java.base@20.0.2/sun.nio.fs.WindowsPathParser.parse(WindowsPathParser.java:153)
	at java.base@20.0.2/sun.nio.fs.WindowsPathParser.parse(WindowsPathParser.java:77)
	at java.base@20.0.2/sun.nio.fs.WindowsPath.parse(WindowsPath.java:92)
	at java.base@20.0.2/sun.nio.fs.WindowsFileSystem.getPath(WindowsFileSystem.java:232)
	at java.base@20.0.2/java.nio.file.Path.of(Path.java:148)
	at org.graalvm.nativeimage.driver/com.oracle.svm.driver.NativeImage.expandAsteriskClassPathElement(NativeImage.java:1795)
	at org.graalvm.nativeimage.driver/com.oracle.svm.driver.NativeImage.addCustomImageClasspath(NativeImage.java:1774)
	at org.graalvm.nativeimage.driver/com.oracle.svm.driver.DefaultOptionHandler.processClasspathArgs(DefaultOptionHandler.java:435)
	at org.graalvm.nativeimage.driver/com.oracle.svm.driver.DefaultOptionHandler.consume(DefaultOptionHandler.java:72)
	at org.graalvm.nativeimage.driver/com.oracle.svm.driver.NativeImage$NativeImageArgsProcessor.apply(NativeImage.java:1703)
	at org.graalvm.nativeimage.driver/com.oracle.svm.driver.NativeImage.processNativeImageArgs(NativeImage.java:2016)
	at org.graalvm.nativeimage.driver/com.oracle.svm.driver.NativeImage.completeImageBuild(NativeImage.java:945)
	at org.graalvm.nativeimage.driver/com.oracle.svm.driver.NativeImage.build(NativeImage.java:1592)
	at org.graalvm.nativeimage.driver/com.oracle.svm.driver.NativeImage.performBuild(NativeImage.java:1557)
	at org.graalvm.nativeimage.driver/com.oracle.svm.driver.NativeImage.main(NativeImage.java:1531)
```

internal/native_image/rules.bzl

@@ -21,6 +21,7 @@ _DEFAULT_GVM_REPO = "@graalvm"
 _GVM_TOOLCHAIN_TYPE = "%s//graalvm/toolchain" % _RULES_REPO
 _BAZEL_CPP_TOOLCHAIN_TYPE = "@bazel_tools//tools/cpp:toolchain_type"
 _BAZEL_CURRENT_CPP_TOOLCHAIN = "@bazel_tools//tools/cpp:current_cc_toolchain"
+_WINDOWS_CONSTRAINT = "@platforms//os:windows"
 
 _PASSTHRU_ENV_VARS = [
     "INCLUDE",
@@ -89,6 +90,9 @@ _NATIVE_IMAGE_ATTRS = {
     "_cc_toolchain": attr.label(
         default = Label(_BAZEL_CURRENT_CPP_TOOLCHAIN),
     ),
+    "_windows_constraint": attr.label(
+        default = Label(_WINDOWS_CONSTRAINT),
+    ),
 }
 
 def _graal_binary_implementation(ctx):
@@ -199,7 +203,15 @@ def _graal_binary_implementation(ctx):
 
     args = ctx.actions.args()
     args.add("--no-fallback")
-    args.add("-cp", ":".join([f.path for f in classpath_depset.to_list()]))
+
+    # TODO: This check really should be on the exec platform, not the target platform, but that
+    # requires going through a separate rule. Since GraalVM doesn't support cross-compilation, the
+    # distinction doesn't matter for now.
+    if ctx.target_platform_has_constraint(ctx.attr._windows_constraint[platform_common.ConstraintValueInfo]):
+        path_list_separator = ";"
+    else:
+        path_list_separator = ":"
+    args.add("-cp", path_list_separator.join([f.path for f in classpath_depset.to_list()]))
 
     if gvm_toolchain != None and ctx.attr.pass_compiler_path:
         args.add("--native-compiler-path=%s" % c_compiler_path)