diff --git a/source-builder/config/gdb-common-1.cfg b/source-builder/config/gdb-common-1.cfg
index 9018448..159b8a5 100644
--- a/source-builder/config/gdb-common-1.cfg
+++ b/source-builder/config/gdb-common-1.cfg
@@ -108,8 +108,9 @@
     %define gdb-host-libs -L '%{host_ldflags}'
   %endif
   %if %{gdb-python-config} != %{nil}
-    %define gdb-python-config-libs -l '%(%{gdb-python-config} --ldflags)'
-    %define gdb-python-lib-check %(%{_sbdir}/sb/rtems-build-dep -c %{__cc} %{gdb-host-libs} %{gdb-python-config-libs})
+    %define gdb-python-lib-filter awk 'BEGIN{FS=" "}/python/{for(i=1;i<NF;++i)if(match($i,".*python.*")) print "lib"substr($i,3)"*";}'
+    %define gdb-python-config-libs %(%{gdb-python-config} --ldflags | %{gdb-python-lib-filter})
+    %define gdb-python-lib-check %(%{_sbdir}/sb/rtems-build-dep -c %{__cc} %{gdb-host-libs} -l %{gdb-python-config-libs})
   %else
     %define gdb-python-lib-check %(%{_sbdir}/sb/rtems-build-dep -c %{__cc} %{gdb-host-libs} -l %{gdb-python-ver-lib})
   %endif
diff --git a/source-builder/sb/config.py b/source-builder/sb/config.py
index df81d42..93a74f3 100644
--- a/source-builder/sb/config.py
+++ b/source-builder/sb/config.py
@@ -49,13 +49,17 @@ except:
     sys.exit(1)
 
 def _check_bool(value):
+    istrue = None
     if value.isdigit():
         if int(value) == 0:
             istrue = False
         else:
             istrue = True
     else:
-        istrue = None
+        if type(value) is str and len(value) == 2 and value[0] == '!':
+            istrue = _check_bool(value[1])
+            if type(istrue) is bool:
+                istrue = not istrue
     return istrue
 
 def _check_nil(value):
@@ -416,20 +420,41 @@ class file:
         return macros
 
     def _shell(self, line):
-        sl = self.sf.findall(line)
-        if len(sl):
-            e = execute.capture_execution()
-            for s in sl:
+        #
+        # Parse the line and handle nesting '()' pairs.
+        #
+        def _exec(shell_macro):
+            output = ''
+            if len(shell_macro) > 3:
+                e = execute.capture_execution()
                 if options.host_windows:
-                    cmd = '%s -c "%s"' % (self.macros.expand('%{__sh}'), s[2:-1])
+                    cmd = '%s -c "%s"' % (self.macros.expand('%{__sh}'), shell_macro[2:-1])
                 else:
-                    cmd = s[2:-1]
+                    cmd = shell_macro[2:-1]
                 exit_code, proc, output = e.shell(cmd)
                 log.trace('shell-output: %d %s' % (exit_code, output))
-                if exit_code == 0:
-                    line = line.replace(s, output)
-                else:
-                    raise error.general('shell macro failed: %s:%d: %s' % (s, exit_code, output))
+                if exit_code != 0:
+                    raise error.general('shell macro failed: %s: %d: %s' % (cmd,
+                                                                            exit_code,
+                                                                            output))
+            return output
+
+        updating = True
+        while updating:
+            updating = False
+            pos = line.find('%(')
+            if pos >= 0:
+                braces = 0
+                for p in range(pos + 2, len(line)):
+                    if line[p] == '(':
+                        braces += 1
+                    elif line[p] == ')':
+                        if braces > 0:
+                            braces -= 1
+                        else:
+                            line = line[:pos] + _exec(line[pos:p + 1]) + line[p + 1:]
+                            updating = True
+                            break
         return line
 
     def _pkgconfig_check(self, test):