selftest/fortran-helloworld: Fix buildpaths error

There is a buildpaths QA error in the test recipe that somehow didn't show up
in earlier testing. Use a source directory and tweak the build command to
avoid embedding build paths in the generated binary.

(From OE-Core rev: 8f1cfaf2be834217cd1cf5be98f44270c36cc31a)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-selftest/recipes-test/fortran/fortran-helloworld.bb

@@ -6,12 +6,15 @@ DEPENDS = "libgfortran"
 
 SRC_URI = "file://hello.f95"
 
+S = "${WORKDIR}/sources"
+UNPACKDIR = "${S}"
+
 # These set flags that Fortran doesn't support
 SECURITY_CFLAGS = ""
 SECURITY_LDFLAGS = ""
 
 do_compile() {
-	${FC} ${LDFLAGS} ${UNPACKDIR}/hello.f95 -o ${B}/fortran-hello
+	${FC} ${LDFLAGS} hello.f95 -o ${B}/fortran-hello
 }
 
 do_install() {