This is based on the respectve patch from NixPkgs, but with the parts pinning
mysql and postgresql executables removed. See our package definition on why.

diff --git a/src/akonadicontrol/agentmanager.cpp b/src/akonadicontrol/agentmanager.cpp
--- a/src/akonadicontrol/agentmanager.cpp
+++ b/src/akonadicontrol/agentmanager.cpp
@@ -47,7 +47,7 @@ public:
         connect(this, &Akonadi::ProcessControl::unableToStart, this, []() {
             QCoreApplication::instance()->exit(255);
         });
-        start(QStringLiteral("akonadiserver"), args, RestartOnCrash);
+        start(QStringLiteral(NIX_OUT "/bin/akonadiserver"), args, RestartOnCrash);
     }

     ~StorageProcessControl() override
@@ -69,7 +69,7 @@ public:
         connect(this, &Akonadi::ProcessControl::unableToStart, this, []() {
             qCCritical(AKONADICONTROL_LOG) << "Failed to start AgentServer!";
         });
-        start(QStringLiteral("akonadi_agent_server"), args, RestartOnCrash);
+        start(QStringLiteral(NIX_OUT "/bin/akonadi_agent_server"), args, RestartOnCrash);
     }

     ~AgentServerProcessControl() override
diff --git a/src/akonadicontrol/agentprocessinstance.cpp b/src/akonadicontrol/agentprocessinstance.cpp
--- a/src/akonadicontrol/agentprocessinstance.cpp
+++ b/src/akonadicontrol/agentprocessinstance.cpp
@@ -62,7 +62,7 @@ bool AgentProcessInstance::start(const AgentType &agentInfo)
     } else {
         Q_ASSERT(agentInfo.launchMethod == AgentType::Launcher);
         const QStringList arguments = QStringList() << executable << identifier();
-        const QString agentLauncherExec = Akonadi::StandardDirs::findExecutable(QStringLiteral("akonadi_agent_launcher"));
+        const QString agentLauncherExec = QLatin1String(NIX_OUT "/bin/akonadi_agent_launcher");
         mController->start(agentLauncherExec, arguments);
     }
     return true;
diff --git a/src/server/storage/dbconfigmysql.cpp b/src/server/storage/dbconfigmysql.cpp
--- a/src/server/storage/dbconfigmysql.cpp
+++ b/src/server/storage/dbconfigmysql.cpp
@@ -215,7 +215,7 @@ bool DbConfigMysql::startInternalServer()
 #endif

     // generate config file
-    const QString globalConfig = StandardDirs::locateResourceFile("config", QStringLiteral("mysql-global.conf"));
+    const QString globalConfig = QLatin1String(NIX_OUT "/etc/xdg/akonadi/mysql-global.conf");
     const QString localConfig = StandardDirs::locateResourceFile("config", QStringLiteral("mysql-local.conf"));
     const QString actualConfig = StandardDirs::saveDir("data") + QLatin1String("/mysql.conf");
     if (globalConfig.isEmpty()) {
owmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-04-12 14:12:49 +0200'>2021-04-12</span></td><td><a href='/guix/commit/gnu/tests/docker.scm?id=e1a465209925c43871ce581c2752ae620fbedd3a'>tests: docker: Increase VM building memory size to 1024MiB.</a><span class='msg-avail'>...<span class='msg-tooltip'>This fixes the following error when running the "docker-system" test:

In ice-9/ftw.scm:
   553:30  1 (_ #&lt;directory stream db6660&gt;)
In unknown file:
           0 (readdir #&lt;directory stream db6660&gt;)

ERROR: In procedure readdir:
In procedure readdir: Cannot allocate memory

* gnu/tests/docker.scm (%test-docker-system): Bump image building VM memory
size to 1024 MiB.
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2021-02-25 11:29:35 +0100'>2021-02-25</span></td><td><a href='/guix/commit/gnu/tests/docker.scm?id=2b0026813bc18258dd6fbecd69723df0267994b7'>tests: docker-system: Increase VM memory.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/tests/docker.scm (run-docker-system-test)[vm]: Increase
'memory-size'.
</span></span></td><td>Ludovic Courtès</td></tr>