Add the installation bin directory to the path internally in wrapper scripts

This allows invoking the script frontends via an explicit path,
without adding the directory to the PATH environment variable before
calling them.

wrappers/dlltool-wrapper.sh

@@ -1,5 +1,8 @@
 #!/bin/sh
 
+DIR="$(cd "$(dirname "$0")" && pwd)"
+export PATH=$DIR:$PATH
+
 TARGET="$(basename $0 | sed 's/-[^-]*$//')"
 ARCH=$(echo $TARGET | sed 's/-.*//')
 case $ARCH in

wrappers/ld-wrapper.sh

@@ -1,5 +1,8 @@
 #!/bin/sh
 
+DIR="$(cd "$(dirname "$0")" && pwd)"
+export PATH=$DIR:$PATH
+
 if [ "$1" = "--help" ]; then
     cat<<EOF
 GNU ld impersonation

wrappers/objdump-wrapper.sh

@@ -1,5 +1,8 @@
 #!/bin/sh
 
+DIR="$(cd "$(dirname "$0")" && pwd)"
+export PATH=$DIR:$PATH
+
 if [ "$1" = "-f" ]; then
     # libtool can try to run objdump -f and wants to see certain strings in
     # the output, to accept it being a windows (import) library

wrappers/windres-wrapper.sh

@@ -27,6 +27,9 @@
 #
 # For more information, please refer to <http://unlicense.org/>
 
+DIR="$(cd "$(dirname "$0")" && pwd)"
+export PATH=$DIR:$PATH
+
 print_version () {
     cat <<EOF >&2
 version: LLVM windres (GNU Binutils compatible) 0.1