Initial tweaks to get MSVC working.

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
new file mode 100644
index 0000000..09a8f71
--- /dev/null
+++ b/WORKSPACE
@@ -0,0 +1,2 @@
+# Bazel extensions for pybind11
+workspace(name = "pybind11_bazel")

build_defs.bzl

diff --git a/build_defs.bzl b/build_defs.bzl
index 1e55548..cde1e93 100644
--- a/build_defs.bzl
+++ b/build_defs.bzl
@@ -8,9 +8,12 @@
 def register_extension_info(**kwargs):
     pass
 
-PYBIND_COPTS = [
-    "-fexceptions",
-]
+PYBIND_COPTS = select({
+    "@pybind11//:msvc_compiler": [],
+    "//conditions:default": [
+        "-fexceptions",
+    ],
+})
 
 PYBIND_FEATURES = [
     "-use_header_modules",  # Required for pybind11.
@@ -38,9 +41,15 @@
 
     native.cc_binary(
         name = name + ".so",
-        copts = copts + PYBIND_COPTS + ["-fvisibility=hidden"],
+        copts = copts + PYBIND_COPTS + select({
+            "@pybind11//:msvc_compiler": [],
+            "//conditions:default": [
+                "-fvisibility=hidden",
+            ],
+        }),
         features = features + PYBIND_FEATURES,
         linkopts = linkopts + select({
+            "@pybind11//:msvc_compiler": [],
             "@pybind11//:osx": [],
             "//conditions:default": ["-Wl,-Bsymbolic"],
         }),

pybind11.BUILD

diff --git a/pybind11.BUILD b/pybind11.BUILD
index 4d7d77a..15590aa 100644
--- a/pybind11.BUILD
+++ b/pybind11.BUILD
@@ -7,13 +7,16 @@
 
 exports_files(["LICENSE"])
 
-OPTIONS = [
-    "-fexceptions",
-    # Useless warnings
-    "-Xclang-only=-Wno-undefined-inline",
-    "-Xclang-only=-Wno-pragma-once-outside-header",
-    "-Xgcc-only=-Wno-error",  # no way to just disable the pragma-once warning in gcc
-]
+OPTIONS = select({
+    ":msvc_compiler": [],
+    "//conditions:default": [
+        "-fexceptions",
+        # Useless warnings
+        "-Xclang-only=-Wno-undefined-inline",
+        "-Xclang-only=-Wno-pragma-once-outside-header",
+        "-Xgcc-only=-Wno-error",  # no way to just disable the pragma-once warning in gcc
+    ],
+})
 
 INCLUDES = [
     "include/pybind11/*.h",
@@ -48,6 +51,11 @@
 )
 
 config_setting(
+    name = "msvc_compiler",
+    flag_values = {"@bazel_tools//tools/cpp:compiler": "msvc-cl"},
+)
+
+config_setting(
     name = "osx",
     constraint_values = ["@platforms//os:osx"],
 )

python_configure.bzl

diff --git a/python_configure.bzl b/python_configure.bzl
index 2107022..7c8fa59 100644
--- a/python_configure.bzl
+++ b/python_configure.bzl
@@ -161,6 +161,8 @@
 
     python_bin = repository_ctx.os.environ.get(_PYTHON_BIN_PATH)
     if python_bin != None:
+        if _is_windows(repository_ctx):
+            python_bin = _norm_path(python_bin)
         return python_bin
 
     python_short_name = "python" + repository_ctx.attr.python_version
@@ -179,6 +181,8 @@
     """Gets the bash bin path."""
     bash_bin = repository_ctx.os.environ.get(_BAZEL_SH)
     if bash_bin != None:
+        if _is_windows(repository_ctx):
+            bash_bin = _norm_path(bash_bin)
         return bash_bin
     else:
         bash_bin_path = repository_ctx.which("bash")
@@ -196,6 +200,8 @@
     """Gets the python lib path."""
     python_lib = repository_ctx.os.environ.get(_PYTHON_LIB_PATH)
     if python_lib != None:
+        if _is_windows(repository_ctx):
+            python_lib = _norm_path(python_lib)
         return python_lib
     print_lib = ("<<END\n" +
                  "from __future__ import print_function\n" +
@@ -300,6 +306,8 @@
     """
     python_config = repository_ctx.os.environ.get(_PYTHON_CONFIG_BIN_PATH)
     if python_config != None:
+        if _is_windows(repository_ctx):
+            python_config = _norm_path(python_config)
         return python_config
 
     bin_dir = repository_ctx.path(python_bin).dirname