configure: do not build doc

Fixes:
    http://autobuild.buildroot.org/results/2ec/2ecfb1143ba89ffa5cdc8096bb175b2c396c4670/
    http://autobuild.buildroot.org/results/c49/c497fc446140694084922d51fe6be308ce5c1c1a/
    http://autobuild.buildroot.org/results/434/434b156b5c9b5c7b65ffe6174cf4e029e7e3ffd8/

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

diff -durN ipmiutil-2.9.5.orig/configure.ac ipmiutil-2.9.5/configure.ac
--- ipmiutil-2.9.5.orig/configure.ac	2015-04-06 12:23:01.020731749 +0200
+++ ipmiutil-2.9.5/configure.ac	2015-04-06 12:24:31.181773510 +0200
@@ -55,7 +55,7 @@
 isredhat=0
 init_scripts="scripts/ipmi_port.sh scripts/ipmiutil_evt scripts/ipmiutil_asy scripts/ipmiutil_wdt"
 projdir=`pwd`
-SUBDIR_S="doc scripts lib util"
+SUBDIR_S="scripts lib util"
 os=Linux
 
 # ltmain.sh, config.sub, et al should have been created, but check to be sure.
@@ -161,7 +161,7 @@
 	LANPLUS_SAM="no"
 	LD_SAMX=""
 	CFLAGS="-O2"
-        SUBDIR_S="doc scripts util"
+        SUBDIR_S="scripts util"
 	if test "x$cross_compiling" = "xyes"; then
 	   # cross-compiling, so link with -static (e.g. Android ARM)
 	   CROSS_LFLAGS="-static"