Meta+Ports: Make 'package.sh showproperty' report multiple properties

And use that to avoid shelling out multiple times for checking
properties in lint-ports.py.

Meta/lint-ports.py

@@ -197,16 +197,17 @@ def get_port_properties(port):
     """
 
     props = {}
-    for prop in PORT_PROPERTIES:
+    package_sh_command = f"./package.sh showproperty {' '.join(PORT_PROPERTIES)}"
-        res = subprocess.run(f"cd {port}; exec ./package.sh showproperty {prop}", shell=True, capture_output=True)
+    res = subprocess.run(f"cd {port}; exec {package_sh_command}", shell=True, capture_output=True)
     if res.returncode == 0:
-            props[prop] = res.stdout.decode('utf-8').strip()
+        results = res.stdout.decode('utf-8').split('\n\n')
+        props = {prop: results[i].strip() for i, prop in enumerate(PORT_PROPERTIES)}
     else:
         print((
-                f'Executing "./package.sh showproperty {prop}" script for port {port} failed with '
+            f'Executing "{package_sh_command}" script for port {port} failed with '
             f'exit code {res.returncode}, output from stderr:\n{res.stderr.decode("utf-8").strip()}'
         ))
-            props[prop] = ''
+        props = {x: '' for x in PORT_PROPERTIES}
     return props
 
 

Ports/.port_include.sh

@@ -543,6 +543,7 @@ do_uninstall() {
     uninstall
 }
 do_showproperty() {
+    while [ $# -gt 0 ]; do
         if ! declare -p "${1}" > /dev/null 2>&1; then
             echo "Property '$1' is not set." >&2
             exit 1
@@ -555,6 +556,9 @@ do_showproperty() {
         else
             echo ${!1}
         fi
+        printf '\n'
+        shift
+    done
 }
 do_all() {
     do_installdepends