Check Source header for mandarory tags

Generating mandatory tags dynamically has them missing in SRPMs if build
with rpmbuid -bs or such. To prevent this from happening check the
source header right after the initial parse run of the spec file. This is
more strict than before relaxing this for the dynamic spec feature as now
errors can come up even if no package is actually build.

Resolves: rpm-software-management#3096

build/parseSpec.c

@@ -677,13 +677,14 @@ static const rpmTagVal sourceTags[] = {
     0
 };
 
-static void initSourceHeader(rpmSpec spec)
+static int initSourceHeader(rpmSpec spec)
 {
     Package sourcePkg = spec->sourcePackage;
     struct Source *srcPtr;
+    int rc = 0;
 
     if (headerIsEntry(sourcePkg->header, RPMTAG_NAME))
-	return;
+	return rc;
 
     char *os = rpmExpand("%{_target_os}", NULL);
     headerPutString(sourcePkg->header, RPMTAG_OS, os);
@@ -739,6 +740,10 @@ static void initSourceHeader(rpmSpec spec)
 		spec->noSource ? "no" : "");
 	free(nvr);
     }
+
+    rc = checkForRequired(spec->sourcePackage->header);
+
+    return rc;
 }
 
 static void finalizeSourceHeader(rpmSpec spec)
@@ -1320,7 +1325,8 @@ static rpmSpec parseSpec(const char *specFile, rpmSpecFlags flags,
 	goto errxit;
 
     /* Assemble source header from parsed components */
-    initSourceHeader(spec);
+    if (initSourceHeader(spec))
+	goto errxit;
     return spec;
 
 errxit: