This is based on the respectve patch from NixPkgs, but with the parts pinning
mysql and postgresql executables removed. The 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
@@ -61,7 +61,7 @@ public:
                 []() {
                     QCoreApplication::instance()->exit(255);
                 });
-        start(QStringLiteral("akonadiserver"), args, RestartOnCrash);
+        start(QLatin1String(NIX_OUT "/bin/akonadiserver"), args, RestartOnCrash);
     }
 
     ~StorageProcessControl() override
@@ -84,7 +84,7 @@ public:
                 []() {
                     qCCritical(AKONADICONTROL_LOG) << "Failed to start AgentServer!";
                 });
-        start(QStringLiteral("akonadi_agent_server"), args, RestartOnCrash);
+        start(QLatin1String(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
@@ -209,7 +209,7 @@ 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()) {
wrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/datastructures.scm?id=67c30ff8ad2c729417c9ae24320552e163816a69&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-05-21 00:17:21 +0200'>2022-05-21</span></td><td><a href='/guix/commit/gnu/packages/datastructures.scm?id=59e8037312aa69b578fcba72da541d4296f62a8f'>gnu: liburcu: Fix license</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/datastructures.scm (liburcu): Fix license.
  [license]: Set to lgpl2.1 and expat.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Olivier Dion</td></tr>
<tr><td><span title='2022-03-28 21:34:08 +0300'>2022-03-28</span></td><td><a href='/guix/commit/gnu/packages/datastructures.scm?id=f24ddb1e90909e12b4a72407fa2a325e452b13d7'>gnu: sdsl-lite: Adjust inputs.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/datastructures.scm (sdsl-lite)[native-inputs]: Move
libdivsufsort from here ...
[propagated-inputs]: ... to here.
</span></span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2022-01-07 02:41:16 +0100'>2022-01-07</span></td><td><a href='/guix/commit/gnu/packages/datastructures.scm?id=6d4573250d1a0678c66d46a55a45139a063800d7'>gnu: liburcu: Update to 0.13.1.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/datastructures.scm (liburcu): Update to 0.13.1.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>