run sed for adjusting specs, fix header installation, add sources to sources.list, fix typos.

[gottaeat]

• updated the kernel source to point to 5.2.11 instead of 5.1.16 or 5.2.10.
• added all of the mentioned source files to sources.list
• fixed the header installation by removing ARCH=${MLFS_CPU} in front of make.
• added a sed command to change /lib/ld-musl-x86_64.so.1//lib/ld-musl-i386.so.1 to /tools/lib/ld-musl-x86_64.so.1//tools/lib/ld-musl-i386.so.1.
• added a grep to check manually for the changes made by the sed oneliner.
• added missing line for for x86_64 in toolchain sanity check, [Requesting program interpreter: /tools/lib/ld-musl-x86_64.so.1].
• fixed a typo to patches from pstches when patching coreutils-8.31.
• instructions for building grep mentions 3.3 in the title but the link is to 3.1, changed the link to point to http://ftp.gnu.org/gnu/grep/grep-3.3.tar.xz.

apologies for:

• the previous accidental pull request to master instead of stable-5.00.
• multiple separated and poorly named commits. properly renamed commits locally.

[dslm4515]

removed ARCH=${MLFS_CPU} from kernel header make, causes errors. actually, wrong variable was used. Command should be: ARCH=${MLFS_ARCH} INSTALL_HDR_PATH=dest headers_install

I am planning to includearmv7l support, so ARCH would then need to be set to arm

[dslm4515]

Otherwise, i like the changes!