tools: allow scripts to run from anywhere

Make the `update-cares.sh`, `update-llhttp.sh`, `update-nghttp2.sh`,
and `update-npm.sh` scripts work even if they are run outside of the
`tools` directory.

PR-URL: #45361
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Zeyu "Alex" Yang <himself65@outlook.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

tools/update-cares.sh

@@ -2,7 +2,7 @@
 set -e
 # Shell script to update c-ares in the source tree to a specific version
 
-BASE_DIR="$( pwd )"
+BASE_DIR=$(cd "$(dirname "$0")/.." && pwd)
 DEPS_DIR="$BASE_DIR/deps"
 ARES_VERSION=$1
 

tools/update-llhttp.sh

@@ -3,7 +3,7 @@ set -e
 
 # Shell script to update llhttp in the source tree to specific version
 
-BASE_DIR="$( pwd )"
+BASE_DIR=$(cd "$(dirname "$0")/.." && pwd)
 DEPS_DIR="${BASE_DIR}/deps"
 LLHTTP_VERSION="$1"
 

tools/update-nghttp2.sh

@@ -2,7 +2,7 @@
 set -e
 # Shell script to update nghttp2 in the source tree to specific version
 
-BASE_DIR="$( pwd )"
+BASE_DIR=$(cd "$(dirname "$0")/.." && pwd)
 DEPS_DIR="$BASE_DIR/deps"
 NGHTTP2_VERSION=$1
 

tools/update-npm.sh

@@ -2,7 +2,7 @@
 set -e
 # Shell script to update npm in the source tree to a specific version
 
-BASE_DIR="$( pwd )"
+BASE_DIR=$(cd "$(dirname "$0")/.." && pwd)
 DEPS_DIR="$BASE_DIR/deps"
 NPM_VERSION=$1