[m-rev.] diff: fix source distribution builds

[Julien Fischer]

Fix source distribution builds.

browser/Mmakefile:
compiler/Mmakefile:
      Restore the .PHONY directives on the Mercury.modules target as their
      absence is causing the source distribution builds to fail.

      Add an XXX comment about this.

Julien.

diff --git a/browser/Mmakefile b/browser/Mmakefile
index 4de0541..3acab92 100644
--- a/browser/Mmakefile
+++ b/browser/Mmakefile
@@ -166,6 +166,9 @@ depend_aux: browse_test.depend declarative_test.depend
  # This directory contains source files for which the module name
  # does not match the file name, so smart recompilation won't work
  # without the Mercury.modules file.
+# XXX this .PHONY directive is required when building the source
+# distribution -- why?
+.PHONY: Mercury.modules
  Mercury.modules: MDB_FLAGS
  	$(MC) $(ALL_GRADEFLAGS) $(ALL_MCFLAGS) -f *.m

diff --git a/compiler/Mmakefile b/compiler/Mmakefile
index 8461b94..fda76ef 100644
--- a/compiler/Mmakefile
+++ b/compiler/Mmakefile
@@ -93,6 +93,9 @@ $(MC_PROG).depend: Mercury.modules COMP_FLAGS
  # This directory contains source files for which the module
  # name doesn't match the file name, so smart recompilation
  # won't work without the Mercury.modules file.
+# XXX this .PHONY directive is required when building the source
+# distribution -- why?
+.PHONY: Mercury.modules
  Mercury.modules: COMP_FLAGS
  	$(MC) $(ALL_GRADEFLAGS) $(ALL_MCFLAGS) -f *.m