buildDotnetModule: do not run dotnet command using env

There should be no reason to use env here:

1. In places where it is used to run dotnet with environment variables,
   the same can be done with shell syntax.

   For example, `env "FOO=$bar" baz` is equivalent to `FOO="$bar" baz`.

2. Otherwise, it just unnecessarily forces PATH lookup for dotnet
   command. In addition to that, some dotnet invocations did not use
   env.

pkgs/build-support/dotnet/build-dotnet-module/hooks/dotnet-build-hook.sh

@@ -41,7 +41,7 @@ dotnetBuildHook() {
             runtimeIdFlags+=("--runtime @runtimeId@")
         fi
 
-        env dotnet build ${project-} \
+        dotnet build ${project-} \
             -maxcpucount:$maxCpuFlag \
             -p:BuildInParallel=$parallelBuildFlag \
             -p:ContinuousIntegrationBuild=true \

pkgs/build-support/dotnet/build-dotnet-module/hooks/dotnet-check-hook.sh

@@ -22,7 +22,7 @@ dotnetCheckHook() {
             runtimeIdFlags=("--runtime @runtimeId@")
         fi
 
-        env "LD_LIBRARY_PATH=@libraryPath@" \
+        LD_LIBRARY_PATH="@libraryPath@" \
             dotnet test "$project" \
               -maxcpucount:$maxCpuFlag \
               -p:ContinuousIntegrationBuild=true \

pkgs/build-support/dotnet/build-dotnet-module/hooks/dotnet-configure-hook.sh

@@ -15,7 +15,7 @@ dotnetConfigureHook() {
 
     dotnetRestore() {
         local -r project="${1-}"
-        env dotnet restore ${project-} \
+        dotnet restore ${project-} \
             -p:ContinuousIntegrationBuild=true \
             -p:Deterministic=true \
             --runtime "@runtimeId@" \
@@ -43,7 +43,7 @@ EOF
     find -name paket.dependencies -exec sed -i 's+source .*+source @nugetSource@/lib+g' {} \;
     find -name paket.lock -exec sed -i 's+remote:.*+remote: @nugetSource@/lib+g' {} \;
 
-    env dotnet tool restore --add-source "@nugetSource@/lib"
+    dotnet tool restore --add-source "@nugetSource@/lib"
 
     (( "${#projectFile[@]}" == 0 )) && dotnetRestore
 

pkgs/build-support/dotnet/build-dotnet-module/hooks/dotnet-install-hook.sh

@@ -27,7 +27,7 @@ dotnetInstallHook() {
             runtimeIdFlags+=("--runtime @runtimeId@")
         fi
 
-        env dotnet publish ${project-} \
+        dotnet publish ${project-} \
             -p:ContinuousIntegrationBuild=true \
             -p:Deterministic=true \
             --output "${installPath-$out/lib/$pname}" \
@@ -40,7 +40,7 @@ dotnetInstallHook() {
 
     dotnetPack() {
         local -r project="${1-}"
-        env dotnet pack ${project-} \
+        dotnet pack ${project-} \
             -p:ContinuousIntegrationBuild=true \
             -p:Deterministic=true \
             --output "$out/share" \