[CRIU] [PATCH 1/2] Makefile.install: cure LIBDIR guessing logic

[Kir Kolyshkin]

Commit 6a51c7e ("make: Allow to install in custom dirs") replaced
all := assignments with ?=, effectively disabling the LIBDIR guessing
logic (as once a variable is assigned, further ?= make no sense).

That commit description says that setting PREFIX from make command line
didn't work. I can't find the original bug report but according to
GNU make documentation (see [1], [2]) as well as to my best knowledge,
any variable set in Makefile can be overridden from the command line,
unless "override VAR = value" is used in the Makefile.

The result of this patch is LIBDIR is correctly set for distros such as
Fedora and Debian, so "make install" works more correct. Surely, any
variable can still be overriden from the command line.

I have also checked the build of Fedora package from criu.spec with this
change -- it works fine.

Now, I am not sure why it was not working for the original bug reporter.
The only hypothesis I have is he tried to do something like

	PREFIX=/usr make

instead of

	make PREFIX=/usr

If this was the case, it was not a bug but wrong usage.

While at it, fix LIBDIR description in INSTALL.md.

[1] https://www.gnu.org/software/make/manual/html_node/Overriding.html
[2] https://www.gnu.org/software/make/manual/html_node/Override-Directive.html

Cc: Cyrill Gorcunov <gorcunov at openvz.org>
Cc: Andrei Vagin <avagin at virtuozzo.com>
Signed-off-by: Kir Kolyshkin <kir at openvz.org>
---
 INSTALL.md       |  2 +-
 Makefile.install | 24 ++++++++++++------------
 2 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/INSTALL.md b/INSTALL.md
index 7a545e8..5987ca5 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -14,7 +14,7 @@ this command accepts the following variables:
  * **SBINDIR**, to specify where to put CRIU executable (`$(PREFIX)/sbin` by default);
  * **MANDIR**, to specify directory for manual pages (`$(PREFIX)/share/man` by default);
  * **SYSTEMDUNITDIR**, to specify place where systemd units are living (`$(PREFIX)/lib/systemd/system` by default);
- * **LIBDIR**, to specify directory where to put libraries (`$(PREFIX)/lib` by default).
+ * **LIBDIR**, to specify directory where to put libraries (guess the correct path  by default).
 
 Thus one can type
 
diff --git a/Makefile.install b/Makefile.install
index a16614b..74e433b 100644
--- a/Makefile.install
+++ b/Makefile.install
@@ -1,25 +1,25 @@
 #
 # Installation paths.
-PREFIX		?= /usr/local
-BINDIR		?= $(PREFIX)/bin
-SBINDIR		?= $(PREFIX)/sbin
-MANDIR		?= $(PREFIX)/share/man
-SYSTEMDUNITDIR	?= $(PREFIX)/lib/systemd/system
-LOGROTATEDIR	?= $(PREFIX)/etc/logrotate.d
-LIBDIR		?= $(PREFIX)/lib
-INCLUDEDIR	?= $(PREFIX)/include
-LIBEXECDIR	?= $(PREFIX)/libexec
+PREFIX		:= /usr/local
+BINDIR		:= $(PREFIX)/bin
+SBINDIR		:= $(PREFIX)/sbin
+MANDIR		:= $(PREFIX)/share/man
+SYSTEMDUNITDIR	:= $(PREFIX)/lib/systemd/system
+LOGROTATEDIR	:= $(PREFIX)/etc/logrotate.d
+LIBDIR		:= $(PREFIX)/lib
+INCLUDEDIR	:= $(PREFIX)/include
+LIBEXECDIR	:= $(PREFIX)/libexec
 
 #
 # For recent Debian/Ubuntu with multiarch support.
-DEB_HOST_MULTIARCH ?= $(shell dpkg-architecture -qDEB_HOST_MULTIARCH 2>/dev/null)
+DEB_HOST_MULTIARCH := $(shell dpkg-architecture -qDEB_HOST_MULTIARCH 2>/dev/null)
 ifneq "$(DEB_HOST_MULTIARCH)" ""
-        LIBDIR			?= $(PREFIX)/lib/$(DEB_HOST_MULTIARCH)
+        LIBDIR			:= $(PREFIX)/lib/$(DEB_HOST_MULTIARCH)
 else
         #
         # For most other systems
         ifeq "$(shell uname -m)" "x86_64"
-                LIBDIR		?= $(PREFIX)/lib64
+                LIBDIR		:= $(PREFIX)/lib64
         endif
 endif
 
-- 
2.9.3