recipes-devtools: add stb recipe from meta-imx

Even though this recipe is part of NXP's meta-sdk layer instead of the meta-ml
one, it's required to build some of the machine learning packages.

https://jira.digi.com/browse/DEL-7473
https://jira.digi.com/browse/DEL-7484

Signed-off-by: Gabriel Valcazar <gabriel.valcazar@digi.com>

meta-digi-dey/recipes-devtools/stb/stb_git.bb

@@ -0,0 +1,20 @@
+SUMMARY = "single-file public domain (or MIT licensed) libraries for C/C++"
+LICENSE = "MIT"
+LIC_FILES_CHKSUM = "file://stb.h;beginline=14418;endline=14433;md5=b10975d4c8155af1811ab611586f01d2"
+
+PV = "0.0+git${SRCPV}"
+
+SRCREV = "f67165c2bb2af3060ecae7d20d6f731173485ad0"
+SRC_URI = "git://github.com/nothings/stb.git"
+
+S = "${WORKDIR}/git"
+
+do_install() {
+    install -d ${D}${includedir}
+    for hdr in ${S}/*.h; do
+        install -m 0644 $hdr ${D}${includedir}
+    done
+}
+
+# This is a header-only library, so the main package will be empty.
+ALLOW_EMPTY_${PN} = "1"