go-modules/packages: Improve `checkFlags` handling

- Fix handling of `checkFlags` derivation attribute when it's a list of
  two or more elements.

- Improve the readability go `buildGoDir` function with flag array
  building and "test" command conditional.

- Bash style: Single line local assignment of positional parameters.

pkgs/development/go-modules/generic/default.nix

@@ -181,12 +181,22 @@ let
       exclude+='\)'
 
       buildGoDir() {
-        local d; local cmd;
-        cmd="$1"
-        d="$2"
+        local cmd="$1" dir="$2"
+
         . $TMPDIR/buildFlagsArray
+
+        declare -a flags
+        flags+=($buildFlags "''${buildFlagsArray[@]}")
+        flags+=(''${tags:+-tags=${lib.concatStringsSep "," tags}})
+        flags+=(''${ldflags:+-ldflags="$ldflags"})
+        flags+=("-v" "-p" "$NIX_BUILD_CORES")
+
+        if [ "$cmd" = "test" ]; then
+          flags+=($checkFlags)
+        fi
+
         local OUT
-        if ! OUT="$(go $cmd $buildFlags "''${buildFlagsArray[@]}" ''${tags:+-tags=${lib.concatStringsSep "," tags}} ''${ldflags:+-ldflags="$ldflags"} -v -p $NIX_BUILD_CORES $d 2>&1)"; then
+        if ! OUT="$(go $cmd "''${flags[@]}" $dir 2>&1)"; then
           if ! echo "$OUT" | grep -qE '(no( buildable| non-test)?|build constraints exclude all) Go (source )?files'; then
             echo "$OUT" >&2
             return 1
@@ -244,7 +254,7 @@ let
       runHook preCheck
 
       for pkg in $(getGoDirs test); do
-        buildGoDir test $checkFlags "$pkg"
+        buildGoDir test "$pkg"
       done
 
       runHook postCheck

pkgs/development/go-packages/generic/default.nix

@@ -160,12 +160,22 @@ let
       exclude+='\)'
 
       buildGoDir() {
-        local d; local cmd;
-        cmd="$1"
-        d="$2"
+        local cmd="$1" dir="$2"
+
         . $TMPDIR/buildFlagsArray
+
+        declare -a flags
+        flags+=($buildFlags "''${buildFlagsArray[@]}")
+        flags+=(''${tags:+-tags=${lib.concatStringsSep "," tags}})
+        flags+=(''${ldflags:+-ldflags="$ldflags"})
+        flags+=("-v" "-p" "$NIX_BUILD_CORES")
+
+        if [ "$cmd" = "test" ]; then
+          flags+=($checkFlags)
+        fi
+
         local OUT
-        if ! OUT="$(go $cmd $buildFlags "''${buildFlagsArray[@]}" ''${tags:+-tags=${lib.concatStringsSep "," tags}} ''${ldflags:+-ldflags="$ldflags"} -v -p $NIX_BUILD_CORES $d 2>&1)"; then
+        if ! OUT="$(go $cmd "''${flags[@]}" $dir 2>&1)"; then
           if ! echo "$OUT" | grep -qE '(no( buildable| non-test)?|build constraints exclude all) Go (source )?files'; then
             echo "$OUT" >&2
             return 1
@@ -225,7 +235,7 @@ let
       runHook preCheck
 
       for pkg in $(getGoDirs test); do
-        buildGoDir test $checkFlags "$pkg"
+        buildGoDir test "$pkg"
       done
 
       runHook postCheck