Makefile: Use the kroki service to generate diagrams

It allows us to have the asciidoctor diagram properly visible from
github and from the generated PDF.

Signed-off-by: Samuel Ortiz <sameo@rivosinc.com>

Makefile

@@ -36,18 +36,20 @@ ASCIIDOCTOR_PDF := asciidoctor-pdf
 ASCIIDOCTOR_HTML := asciidoctor
 OPTIONS := --trace \
            -a compress \
+           -a allow-uri-read \
            -a mathematical-format=svg \
            -a revnumber=${VERSION} \
            -a revremark=${REVMARK} \
            -a revdate=${DATE} \
            -a pdf-fontsdir=docs-resources/fonts \
            -a pdf-theme=docs-resources/themes/riscv-pdf.yml \
            $(XTRA_ADOC_OPTS) \
-		   -D build \
+           -D build \
            --failure-level=ERROR
 REQUIRES := --require=asciidoctor-bibtex \
             --require=asciidoctor-diagram \
-            --require=asciidoctor-mathematical
+            --require=asciidoctor-mathematical \
+            --require=asciidoctor-kroki
 
 .PHONY: all build clean build-container build-no-container build-docs