installsrc: disable AOT for the install-from-source build

Native AOT links the published binary with clang. Leaving it on for a
source install would force every distro to install a C toolchain just
to build a local copy, which is why the install-from-source validation
fails across the board with "gcc or clang is missing".

Installing from source does not need a native binary, so turn AOT off
for it alone: set PublishAot=false in the environment for the build
(the executable project honours an externally supplied value, and the
nested publish inherits it through the packaging scripts). With AOT
off, layout.sh's existing self-contained, single-file publish produces
a portable binary that needs only the .NET SDK to build and bundles its
own runtime to run - so it launches even on the distros where the SDK
was installed to a non-standard location. The shipped packages set
nothing and still default to AOT.

This is a deliberate stopgap that leaves the rest of the
install-from-source flow as-is; a later commit reworks
install-from-source handling altogether.

Assisted-by: Claude Opus 4.8
Signed-off-by: Matthew John Cheetham <mjcheetham@outlook.com>

Author: mjcheetham

src/linux/Packaging.Linux/install-from-source.sh

@@ -259,5 +259,9 @@ if [ -z "$DOTNET_ROOT" ]; then
 fi
 
 cd "$toplevel_path"
-$sudo_cmd env "PATH=$PATH" $DOTNET_ROOT/dotnet build ./src/linux/Packaging.Linux/Packaging.Linux.csproj -c Release -p:InstallFromSource=true -p:installPrefix=$installPrefix
+# Build a non-AOT binary so installing from source needs only the .NET SDK,
+# not a C toolchain (clang + zlib) to link a native build. PublishAot is read
+# from the environment by Git-Credential-Manager.csproj and inherited by the
+# nested publish.
+$sudo_cmd env "PATH=$PATH" PublishAot=false $DOTNET_ROOT/dotnet build ./src/linux/Packaging.Linux/Packaging.Linux.csproj -c Release -p:InstallFromSource=true -p:installPrefix=$installPrefix
 add_to_PATH "$installPrefix/bin"

src/shared/Git-Credential-Manager/Git-Credential-Manager.csproj

@@ -10,7 +10,10 @@
     <IsTestProject>false</IsTestProject>
     <LangVersion>latest</LangVersion>
     <TargetLatestRuntimePatch>true</TargetLatestRuntimePatch>
-    <PublishAot>true</PublishAot>
+    <!-- Produce a native AOT build by default. Building from source can set
+         PublishAot=false in the environment to opt out, so installing locally
+         doesn't require a C toolchain (clang + zlib) just to link. -->
+    <PublishAot Condition="'$(PublishAot)' == ''">true</PublishAot>
   </PropertyGroup>
 
   <ItemGroup>