[nfc] Improve how formatting works

Change formatting from overwriting the original file to computing a diff
and then applying it.  This improves the workflow in two ways: (1) editors
better handle a patch application as opposed to a file rewrite and (2) if
there is no formatting change, then a rebuild is no longer required.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Makefile

@@ -14,7 +14,7 @@ clean:
 	rm -rf build
 
 format:
-	find . -type f -name '*.md'	| xargs -IX pandoc -o X --wrap=preserve -t markdown+pipe_tables-multiline_tables-grid_tables X
+	find . -type f -name '*.md' -exec ./scripts/format.sh {} ';'
 
 images: $(IMG_EPSS) $(IMG_PNGS)
 

scripts/format.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+
+diff $1 <(pandoc --wrap=preserve -t markdown+pipe_tables-multiline_tables-grid_tables $1) | \
+  patch $1 -