build.sh: delete outdated SKIP_IDCHECK parameter

Commit 1accb3e removed the parameter SKIP_IDCHECK. Remove it from
build.sh and INSTALL in order to avoid confusion.

Link: https://lore.kernel.org/ltp/SEZPR01MB4527B0054808F801B05EECB7A8DE2@SEZPR01MB4527.apcprd01.prod.exchangelabs.com/
Fixes: 1accb3e ("Makefile: Remove IDcheck.sh")
Reviewed-by: Adrian Huang <[email protected]>
Reviewed-by: Li Wang <[email protected]>
Reviewed-by: Petr Vorel <[email protected]>
Signed-off-by: Jiwei Sun <[email protected]>

INSTALL

@@ -55,13 +55,10 @@ in the same directory where the source files reside.
 	$ make all
 	$ make \
 	  "DESTDIR=$SYSROOT" \
-	  SKIP_IDCHECK=[0|1] \
 	  install
 
 - Specifying DESTDIR is optional, but required when installing to a non-host
   sysroot, as opposed to the host system's sysroot.
-- Specify SKIP_IDCHECK=1 if and when you don't want to modify /etc/{group,passwd}
-  on the target system's sysroot.
 
 If you get a build error, please report it to [email protected] with
 following information,
@@ -95,13 +92,10 @@ items which need fixing in the LTP tree.
 	  "top_srcdir=$TOP_SRCDIR" \
 	  "top_builddir=$OUT_OF_BUILD_TREE_DIR" \
 	  "DESTDIR=$SYSROOT" \
-	  SKIP_IDCHECK=[0|1]
 	  install
 
 - Specifying DESTDIR is optional, but required when installing to a non-host
   sysroot, as opposed to the host system's sysroot.
-- Specify SKIP_IDCHECK=1 if and when you don't want to modify /etc/{group,passwd}
-  on the target system's sysroot.
 
 Quick Start
 -----------

build.sh

@@ -138,7 +138,7 @@ install_in_tree()
 install_out_tree()
 {
 	cd $BUILD_DIR
-	make $MAKE_OPTS_OUT_TREE DESTDIR="$prefix" SKIP_IDCHECK=1 install
+	make $MAKE_OPTS_OUT_TREE DESTDIR="$prefix" install
 }
 
 usage()