as: add page (#2128)

pages/osx/as.md

@@ -0,0 +1,20 @@
+# as
+
+> Portable GNU assembler.
+> Primarily intended to assemble output from `gcc` to be used by `ld`.
+
+- Assemble a file, writing the output to a.out:
+
+`as {{file.s}}`
+
+- Assemble the output to a given file:
+
+`as {{file.s}} -o {{out.o}}`
+
+- Generate output faster by skipping whitespace and comment preprocessing. (Should only be used for trusted compilers):
+
+`as -f {{file.s}}`
+
+- Include a given path to the list of directories to search for files specified in .include directives:
+
+`as -I {{path/to/directory}} {{file.s}}`