Exclude WORKDIR from recipe stamps, allowing caching

During install of rust-bin and cargo-bin binaries are placed into ${S},
which itself builds on ${WORKDIR}. Normally ${WORKDIR} is ignored for
sstate cache but it is not being ignored properly in rust-bin and
cargo-bin for two different reasons:

In rust-bin, a dependency is being created on the value of ${S} instead
of creating a transitive dependency on ${S} -> ${WORKDIR} and then
ignoring ${WORKDIR}. It's not clear why exactly this is the case, but it
was confirmed by looking at the output of the stamps for the rust-bin
recipe. The fix is to explicitly exclude ${WORKDIR} from the creation of
${S} with a `vardepsexclude`

In cargo-bin the issue is more straight-forward: the ${S} value was
being explicitly assembled in Python code, so Bitbake never sees that
${S} is formed from ${WORKDIR}. Adding explicit `vardeps` and
`vardepsexcludes` in the Python section fixes this.

Signed-off-by: Nick Stevens <[email protected]>

Author: nastevens

recipes-devtools/rust/cargo-bin-cross.inc

@@ -36,6 +36,9 @@ python () {
                  (cargo_url(target), cargo_md5(target), cargo_sha256(target),
                   d.getVar("PN", True) + "-" + pv + "-" + target + ".tar.gz"))
     src_uri = d.getVar("SRC_URI", True).split()
+    cargo_extract_path = cargo_url(target).split('/')[-1].replace('.tar.gz', '')
     d.setVar("SRC_URI", ' '.join(src_uri + [cargo_uri]))
-    d.setVar("S", "{}/{}".format(d.getVar("WORKDIR", True), cargo_url(target).split('/')[-1].replace('.tar.gz', '')))
+    d.setVar("S", "${{WORKDIR}}/{}".format(cargo_extract_path))
+    d.appendVarFlag("S", "vardeps", " cargo_url")
+    d.appendVarFlag("S", "vardepsexclude", " WORKDIR")
 }

recipes-devtools/rust/rust-bin-cross.inc

@@ -22,6 +22,9 @@ RUST_ALL_TARGETS = "${RUST_BUILD_TARGET} ${RUST_TARGET_TARGET} ${EXTRA_RUST_TARG
 
 S = "${WORKDIR}/rustc-${PV}-${RUST_BUILD_TARGET}"
 
+# Relocating WORKDIR doesn't matter to installer
+S[vardepsexclude] += "WORKDIR"
+
 SYSROOT_DIRS_NATIVE += "${prefix}"
 SYSROOT_DIRS_BLACKLIST += "\
     ${prefix}/share \