make -r world: build failed. Please re-run make with V=s [solution]

when i tried to compile openWRT for the first time i had the following errors

make[3]: Leaving directory `/home/oghazal/Desktop/openWRT/trunk/tools/missing-macros'
make[3]: Entering directory `/home/oghazal/Desktop/openWRT/trunk/tools/cmake'
mkdir -p /home/oghazal/Desktop/openWRT/trunk/dl
/home/oghazal/Desktop/openWRT/trunk/scripts/download.pl "/home/oghazal/Desktop/openWRT/trunk/dl" "cmake-2.8.9.tar.gz" "801f4c87f8b604f727df5bf1f05a59e7" "http://www.cmake.org/files/v2.8/"
--2012-10-15 16:54:18--  http://www.cmake.org/files/v2.8/cmake-2.8.9.tar.gz
Resolving www.cmake.org... 66.194.253.19
Connecting to www.cmake.org|66.194.253.19|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 26570240 (25M) [application/x-gzip]
Saving to: `STDOUT'

100%[=======================================>] 26,570,240  10.2M/s   in 2.5s   

2012-10-15 16:54:21 (10.2 MB/s) - written to stdout [26570240/26570240]

MD5 sum of the downloaded file does not match (file: 685d9d1fb6538b5ec03d67f54137685e, requested: 801f4c87f8b604f727df5bf1f05a59e7) - deleting download.
--2012-10-15 16:54:21--  http://mirror2.openwrt.org/sources/cmake-2.8.9.tar.gz
Resolving mirror2.openwrt.org... 46.4.11.11
Connecting to mirror2.openwrt.org|46.4.11.11|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2012-10-15 16:54:21 ERROR 404: Not Found.

Download failed.
--2012-10-15 16:54:21--  http://downloads.openwrt.org/sources/cmake-2.8.9.tar.gz
Resolving downloads.openwrt.org... 78.24.191.177
Connecting to downloads.openwrt.org|78.24.191.177|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2012-10-15 16:54:22 ERROR 404: Not Found.

Download failed.
No more mirrors to try - giving up.
make[3]: *** [/home/oghazal/Desktop/openWRT/trunk/dl/cmake-2.8.9.tar.gz] Error 2
make[3]: Leaving directory `/home/oghazal/Desktop/openWRT/trunk/tools/cmake'
make[2]: *** [tools/cmake/compile] Error 2
make[2]: Leaving directory `/home/oghazal/Desktop/openWRT/trunk'
make[1]: *** [/home/oghazal/Desktop/openWRT/trunk/staging_dir/target-mips_r2_uClibc-0.9.33.2/stamp/.tools_install_nnnnn] Error 2
make[1]: Leaving directory `/home/oghazal/Desktop/openWRT/trunk'
make: *** [world] Error 2

so it seems that cmake is not getting downloaded correctly using wget, so to solve this problem we need to download the cmake package manually (using firefox not wget) and then to place it in `trunk/dl` directory and then run `make` again.

Makefile:4: *** missing separator. Stop. [solution]

When i tried to compile a program using a Makefile, i had the following error  

Makefile:4: *** missing separator.  Stop.

  after googling the error i found that `make` does not accept whitespaces and unlike DOS, it is expecting a tab in the beginning of each line.

so to solution is to replace the whitespaces ( in this case in the 4th line) with a tab.

reference: http://www.delorie.com/djgpp/v2faq/faq22_17.html