use explicit revisions so i can use the docker build cache

docker/scripts/install-dependencies-rtlsdr.sh

@@ -3,6 +3,9 @@ set -euxo pipefail
 
 function cmakebuild() {
   cd $1
+  if [[ ! -z "${2:-}" ]]; then
+    git checkout $2
+  fi
   mkdir build
   cd build
   cmake ..
@@ -20,7 +23,7 @@ BUILD_PACKAGES="git libusb-dev cmake make gcc musl-dev g++ linux-headers"
 apk add --no-cache $STATIC_PACKAGES
 apk add --no-cache --virtual .build-deps $BUILD_PACKAGES
 
-git clone --depth 1 https://github.com/osmocom/rtl-sdr.git
-cmakebuild rtl-sdr
+git clone https://github.com/osmocom/rtl-sdr.git
+cmakebuild rtl-sdr b5af355b1d833b3c898a61cf1e072b59b0ea3440
 
 apk del .build-deps