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()) {
04611fefbf268740d'>pidgin-libnm.patch</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/patches/pidgin-libnm.patch?id=0a2e80c369d4beb2073d9d604611fefbf268740d&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-05-24 16:16:14 +0200'>2020-05-24</span></td><td><a href='/guix/commit/gnu/packages/patches/pidgin-libnm.patch?id=4492981706e0f2041053fdc728e29232855d8689'>gnu: pidgin: Fix build with Meson network-manager.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a follow-up commit to 255ff74f3ab514a76068f6cfccc7f8dbcf8b7f3f:
building network-manager with Meson breaks users of NetworkManager.pc.

* gnu/packages/messaging.scm (pidgin)[source]: Add pidgin-libnm.patch.
Force re-bootstrapping in a new snippet.
[native-inputs]: Add autoconf, automake, and libtool.
* gnu/packages/patches/pidgin-libnm.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>