Permit user to suppress passing --prefix to setup.py

We change all invocations of setup.py as follows:

* use $(PYTHON) instead of `python' so that the user can specify
  an alternative python version if they need to.  If not set it
  defaults to `python' in Config.mk.

* pass --prefix=$(PREFIX) via a new make variable
  $(PYTHON_PREFIX_ARG).  This allows a user to suppress the
  --prefix=... argument entirely by setting PYTHON_PREFIX_ARG=''.
  This will work around the bug described here
     https://bugs.launchpad.net/ubuntu/+bug/362570
  where passing --prefix=/usr/local (which ought to have no effect as
  /usr/local is the default prefix) changes which subdirectory
  distutils chooses, and results in the files being installed in
  site-packages which is not on the default search path.

  Users not affected by this python packaging bug should not set
  PYTHON_PREFIX_ARG and their builds will not be affected.  (Provided
  PREFIX did not contain spaces.  People who put spaces in PREFIX are
  being quite optimistic.)

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/Config.mk b/Config.mk
index c1aa25ccd2..214b59296f 100644
--- a/Config.mk
+++ b/Config.mk
@@ -35,6 +35,12 @@ EXTRA_INCLUDES += $(EXTRA_PREFIX)/include
 EXTRA_LIB += $(EXTRA_PREFIX)/$(LIBLEAFDIR)
 endif
 
+PYTHON      ?= python
+PYTHON_PREFIX_ARG ?= --prefix="$(PREFIX)"
+# The above requires that PREFIX contains *no spaces*. This variable is here
+# to permit the user to set PYTHON_PREFIX_ARG to '' to workaround this bug:
+#  https://bugs.launchpad.net/ubuntu/+bug/362570
+
 # cc-option: Check if compiler supports first option, else fall back to second.
 # Usage: cflags-y += $(call cc-option,$(CC),-march=winchip-c6,-march=i586)
 cc-option = $(shell if test -z "`$(1) $(2) -S -o /dev/null -xc \