Simplify GHC packaging by extracting bootstrap and build tools - #203

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@packages/alex/build.sh`:
- Around line 1-12: The build script must change into the extracted, versioned
source directory before building and reference the version variable; update the
top of the script to cd into the directory named by $MINIMAL_ARG_VERSION (e.g.,
cd "${MINIMAL_ARG_VERSION}" or cd "$MINIMAL_ARG_VERSION") before invoking ghc
and the ./Setup commands (Setup.hs, ghc --make Setup.hs, ./Setup
configure/build/copy), ensuring $OUTPUT_DIR is still used for copy destdir.
- Around line 4-10: The build script always compiles "Setup.hs" even when only
"Setup.lhs" exists; update the logic to select the existing setup file and
compile that instead (e.g., determine a SETUP_FILE variable that is "Setup.hs"
if present, otherwise "Setup.lhs", and use that variable in the ghc --make and
./Setup commands). Ensure references to Setup.hs in the compile and run steps
are replaced by this selected setup filename so the path where only Setup.lhs is
provided succeeds.

In `@packages/ghc-bootstrap/build.sh`:
- Around line 27-35: The script hardcodes /usr/lib/libncursesw.so.6 when
creating the libtinfo.so.6 shim; update it to locate the real ncurses library
(search /usr/lib* and /usr/lib64 or use ldconfig -p/grep or gcc
-print-file-name) into a variable (e.g., NCURSES_PATH) and use that variable
when copying to "$OUTPUT_DIR/usr/lib/libtinfo.so.6" and to
"$GHC_LIB_DIR/libtinfo.so.6"; if no library is found, emit a clear error and
exit non‑zero. Ensure you reference OUTPUT_DIR, GHC_LIB_DIR and
MINIMAL_ARG_VERSION and replace the two cp -p /usr/lib/libncursesw.so.6
occurrences with cp -p "$NCURSES_PATH" ... .

In `@packages/ghc/build.sh`:
- Around line 42-46: The current export of LD_LIBRARY_PATH can produce a
trailing colon when LD_LIBRARY_PATH is unset, causing ld.so to treat it as the
current directory; update the export that sets LD_LIBRARY_PATH (the line using
PSEUDO_LIBS and export LD_LIBRARY_PATH) so it only inserts a ':' between
PSEUDO_LIBS and the existing LD_LIBRARY_PATH when LD_LIBRARY_PATH is non-empty
(i.e., append the old value conditionally via parameter expansion or an
if-check), ensuring no trailing empty entry is added.

In `@packages/happy/build.sh`:
- Around line 1-12: The build script doesn't cd into the extracted versioned
source directory nor reference the MINIMAL_ARG_VERSION variable; update
packages/happy/build.sh to first change directory into the extracted source
(e.g. cd "happy-$MINIMAL_ARG_VERSION" or whichever directory name pattern is
used) before running ghc and ./Setup commands, and replace any hardcoded paths
(if present) with references that use $MINIMAL_ARG_VERSION and keep OUTPUT_DIR
usage for copy/destdir; ensure the cd happens before checking/creating Setup.hs
and before running ghc and ./Setup configure/build/copy.
- Around line 4-10: The build script assumes Setup.hs is present when running
GHC; change the compile step to pick the existing setup file dynamically so
Setup.lhs is handled too: after the block that creates Setup.hs only when
neither file exists, invoke GHC with the actual setup filename (use Setup.lhs if
it exists, otherwise Setup.hs) for the "ghc --make" step, then continue to run
the generated ./Setup configure --prefix=/usr; update the reference to the
compiled filename in the subsequent commands to match the chosen source
(Setup.lhs or Setup.hs).

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@packages/ghc-bootstrap/build.sh`:
- Around line 58-68: The ldconfig pipeline in the NCURSES_PATH fallback can
cause the script to abort under set -euo pipefail; modify the assignment to
LDCONFIG_PATH so pipeline failures don't propagate (e.g. replace the pipeline
with a single awk that matches and exits: ldconfig -p | awk
'/libncursesw.so.6|libncurses.so.6/ {print $NF; exit}' or append "|| true" to
the command substitution), ensuring LDCONFIG_PATH becomes empty on no-match and
lets the subsequent if [ -f "$LDCONFIG_PATH" ] check run; update the block that
sets NCURSES_PATH from LDCONFIG_PATH accordingly.