mktemp: fix common and standardize between variants (#10700)

* mktemp: fix `common` and standardize variants
* mktemp: add -p example
* linux/mktemp: add -p example
* linux/mktemp: mention `$TMPDIR` in the `-p` example
* osx/mktemp: add page
* linux/mktemp: fix errors
* linux/mktemp: add serial comma

pages/osx/mktemp.md

@@ -0,0 +1,24 @@
+# mktemp
+
+> Create a temporary file or directory.
+> More information: <https://keith.github.io/xcode-man-pages/mktemp.1.html>.
+
+- Create an empty temporary file and print its absolute path:
+
+`mktemp`
+
+- Use a custom directory (defaults to the output of `getconf DARWIN_USER_TEMP_DIR`, or `/tmp`):
+
+`mktemp --tmpdir={{/path/to/tempdir}}`
+
+- Use a custom path template (`X`s are replaced with random alphanumeric characters):
+
+`mktemp {{/tmp/example.XXXXXXXX}}`
+
+- Use a custom file name prefix:
+
+`mktemp -t {{example}}`
+
+- Create an empty temporary directory and print its absolute path:
+
+`mktemp --directory`