diff --git a/Dockerfile b/Dockerfile
index 9011403f..22c7bf34 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,6 +1,5 @@
 FROM alpine
-WORKDIR /mpw/gradle
-ADD . /mpw
 
-RUN apk update && apk add libtool automake autoconf make g++ openjdk8
-RUN ./gradlew -i build
+RUN apk add --no-cache git libtool automake autoconf make g++ bash openjdk8
+RUN git clone --depth=3 $(: --shallow-submodules) --recurse-submodules https://gitlab.com/MasterPassword/MasterPassword.git /mpw
+RUN cd /mpw/gradle && ./gradlew -i clean build
diff --git a/lib/bin/build_lib b/lib/bin/build_lib
index ff2942a8..9ce6c288 100755
--- a/lib/bin/build_lib
+++ b/lib/bin/build_lib
@@ -69,16 +69,15 @@ _initialize_needs() {
 # By default, this will wipe the prefix, run `make distclean` and `git clean -fdx`.
 clean() { _clean "$@"; }
 _clean() {
-    rm -rf "$prefix"
-
     if [[ $platform = windows ]]; then
         printf '"%%VSINSTALLDIR%%\Common7\Tools\VsMSBuildCmd.bat" && msbuild /t:Clean' > .clean.bat
         cmd //c .clean.bat
         rm -f .clean.bat
+    elif [[ -e Makefile ]] && make -s distclean; then :
+    elif [[ -e .git ]] && git clean -fdx; then :
     fi
 
-    [[ ! -e Makefile ]] || make -s distclean
-    [[ ! -e .git ]] || git clean -fdx
+    rm -rf "$prefix"
 }
 
 # prepare <prefix> <platform> [ <arch> ... ]
@@ -104,7 +103,7 @@ _prepare_clean() {
     local prefix=$1 platform=$2; shift 2
 
     rm -rf "$prefix"
-    install -d "$prefix"
+    install -d "$prefix/out"
 }
 
 # prepare_config <prefix> <platform> [ <arch> ... ]
@@ -116,9 +115,14 @@ prepare_config() { _prepare_config "$@"; }
 _prepare_config() {
     local prefix=$1 platform=$2; shift 2
 
-    [[ $platform = windows ]] && return
+    [[ -e "$prefix/out/.prepared" ]] && return
 
-    [[ -e configure ]] || autoreconf --verbose --install --symlink 2> >(sed 's/^\([^:]*\):[0-9]\{1,\}: /\1: /')
+    if [[ $platform = windows ]]; then :
+    else
+        autoreconf --verbose --install --symlink 2> >(sed 's/^\([^:]*\):[0-9]\{1,\}: /\1: /')
+    fi
+
+    touch "$prefix/out/.prepared"
 }
 
 # target <prefix> <platform> <arch>
@@ -142,9 +146,10 @@ target_prepare() { _target_prepare "$@"; }
 _target_prepare() {
     local prefix=$1 platform=$2 arch=$3; shift 3
 
-    [[ $platform = windows ]] && return
-
-    [[ ! -e Makefile ]] || make -s clean
+    if [[ $platform = windows ]]; then :
+    else
+        [[ ! -e Makefile ]] || make -s clean
+    fi
 }
 
 # target_configure <prefix> <platform> <arch> [ <args> ... ]
@@ -220,7 +225,7 @@ _finalize_merge() {
 
     [[ -e "$prefix/$archs/include" ]] && mv -f -- "$prefix/$archs/include" "$prefix/out/"
 
-    mkdir -p "$prefix/out/lib"
+    install -d "$prefix/out/lib"
     case "$platform" in
         'linux')
             for arch in "${archs[@]}"; do
diff --git a/lib/libjson-c b/lib/libjson-c
index e3752b58..3df1f98b 160000
--- a/lib/libjson-c
+++ b/lib/libjson-c
@@ -1 +1 @@
-Subproject commit e3752b58945d23895535857ed136a5185bad02ce
+Subproject commit 3df1f98b4ab52f271dba5e13ec59cf4d1d093e1a
diff --git a/lib/libsodium b/lib/libsodium
index cfb0f947..850edc11 160000
--- a/lib/libsodium
+++ b/lib/libsodium
@@ -1 +1 @@
-Subproject commit cfb0f94704841f943a5a11d9e335da409c55d58a
+Subproject commit 850edc1175c78ed72124cfbef073c7ecc655c476
diff --git a/platform-independent/c/core/build.gradle b/platform-independent/c/core/build.gradle
index 8237f9ad..61128857 100644
--- a/platform-independent/c/core/build.gradle
+++ b/platform-independent/c/core/build.gradle
@@ -67,10 +67,16 @@ library {
                 commandLine 'bash', '-x', "$rootDir/../lib/bin/build_libsodium-${system}"
                 privateHeaders.from "$rootDir/../lib/libsodium/src/libsodium/include"
             }
+            clean.dependsOn project.tasks.maybeCreate( "clean_libsodium-${system}", Exec.class ).configure {
+                commandLine 'bash', '-x', "$rootDir/../lib/bin/build_libsodium-${system}", 'clean'
+            }
             archive.dependsOn project.tasks.maybeCreate( "build_libjson-c-${system}", Exec.class ).configure {
                 commandLine 'bash', '-x', "$rootDir/../lib/bin/build_libjson-c-${system}"
                 privateHeaders.from "$rootDir/../lib/libjson-c/build-${system}~/out"
             }
+            clean.dependsOn project.tasks.maybeCreate( "clean_libjson-c-${system}", Exec.class ).configure {
+                commandLine 'bash', '-x', "$rootDir/../lib/bin/build_libjson-c-${system}", 'clean'
+            }
         }
     }
 }