unix: replace Perl script references in "README.md" with Go programs

Update references to mksyscall*.pl and mksysnum*.pl Perl scripts in
"README.md" with mksyscall*.go and mksysnum*.go Go programs.

Updates golang/go#27779

Change-Id: Ide3f5d9894c91aa6103d6bbe5ec64a47c969daa7
Reviewed-on: https://go-review.googlesource.com/c/162278
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>

unix/README.md

@@ -32,7 +32,7 @@ To build the files for your current OS and architecture, make sure GOOS and
 GOARCH are set correctly and run `mkall.sh`. This will generate the files for
 your specific system. Running `mkall.sh -n` shows the commands that will be run.
 
-Requirements: bash, perl, go
+Requirements: bash, go
 
 ### New Build System (currently for `GOOS == "linux"`)
 
@@ -52,14 +52,14 @@ system and have your GOOS and GOARCH set accordingly. Running `mkall.sh` will
 then generate all of the files for all of the GOOS/GOARCH pairs in the new build
 system. Running `mkall.sh -n` shows the commands that will be run.
 
-Requirements: bash, perl, go, docker
+Requirements: bash, go, docker
 
 ## Component files
 
 This section describes the various files used in the code generation process.
 It also contains instructions on how to modify these files to add a new
 architecture/OS or to add additional syscalls, types, or constants. Note that
-if you are using the new build system, the scripts cannot be called normally.
+if you are using the new build system, the scripts/programs cannot be called normally.
 They must be called from within the docker container.
 
 ### asm files
@@ -81,8 +81,8 @@ each GOOS/GOARCH pair.
 
 ### mksysnum
 
-Mksysnum is a script located at `${GOOS}/mksysnum.pl` (or `mksysnum_${GOOS}.pl`
-for the old system). This script takes in a list of header files containing the
+Mksysnum is a Go program located at `${GOOS}/mksysnum.go` (or `mksysnum_${GOOS}.go`
+for the old system). This program takes in a list of header files containing the
 syscall number declarations and parses them to produce the corresponding list of
 Go numeric constants. See `zsysnum_${GOOS}_${GOARCH}.go` for the generated
 constants.
@@ -92,14 +92,14 @@ new installation of the target OS (or updating the source checkouts for the
 new build system). However, depending on the OS, you make need to update the
 parsing in mksysnum.
 
-### mksyscall.pl
+### mksyscall.go
 
 The `syscall.go`, `syscall_${GOOS}.go`, `syscall_${GOOS}_${GOARCH}.go` are
 hand-written Go files which implement system calls (for unix, the specific OS,
 or the specific OS/Architecture pair respectively) that need special handling
 and list `//sys` comments giving prototypes for ones that can be generated.
 
-The mksyscall.pl script takes the `//sys` and `//sysnb` comments and converts
+The mksyscall.go program takes the `//sys` and `//sysnb` comments and converts
 them into syscalls. This requires the name of the prototype in the comment to
 match a syscall number in the `zsysnum_${GOOS}_${GOARCH}.go` file. The function
 prototype can be exported (capitalized) or not.
@@ -160,7 +160,7 @@ signal numbers, and constants. Generated by `mkerrors.sh` (see above).
 ### `zsyscall_${GOOS}_${GOARCH}.go`
 
 A file containing all the generated syscalls for a specific GOOS and GOARCH.
-Generated by `mksyscall.pl` (see above).
+Generated by `mksyscall.go` (see above).
 
 ### `zsysnum_${GOOS}_${GOARCH}.go`