gnutls: clean up ptest compilation

Don't always build the tests in do_compile, use do_compile_ptest so they
are only built when needed.

(From OE-Core rev: 5f4b10a3361e273d22bc880b4127eb53291be47d)

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-support/gnutls/gnutls_3.8.0.bb

@@ -66,6 +66,10 @@ do_configure:prepend() {
 	done
 }
 
+do_compile_ptest() {
+    oe_runmake -C tests buildtest-TESTS
+}
+
 do_install:append:class-target() {
         if ${@bb.utils.contains('PACKAGECONFIG', 'fips', 'true', 'false', d)}; then
           install -d ${D}${bindir}/bin
@@ -73,10 +77,6 @@ do_install:append:class-target() {
         fi
 }
 
-do_compile:append() {
-        oe_runmake ${PARALLEL_MAKE} -C tests buildtest-TESTS
-}
-
 PACKAGES =+ "${PN}-dane ${PN}-openssl ${PN}-xx ${PN}-fips"
 
 FILES:${PN}-dev += "${bindir}/gnutls-cli-debug"