lmdb package: Fix build with other compilers (#23704)

lmdb hardcodes gcc in its Makefile, so override it.

var/spack/repos/builtin/packages/lmdb/package.py

@@ -23,6 +23,10 @@ class Lmdb(MakefilePackage):
 
     build_directory = 'libraries/liblmdb'
 
+    @property
+    def build_targets(self):
+        return ['CC={0}'.format(spack_cc)]
+
     @property
     def install_targets(self):
         return ['prefix={0}'.format(self.prefix), 'install']