Keep the bundled R on the rpath, and stop makepkg tidying the tree

First run of the actual binary: ldd reported 'libR.so => not found'.

patchelf --set-rpath replaces the existing rpath rather than appending, so
setting it to $PREFIX/lib discarded the -Wl,-rpath the build had given the
JASP binary for the bundled R. Every other bundled library resolved; only R
went missing, because libR.so/libRblas.so/libRlapack.so live under
R/lib/R/lib rather than in the bundled lib directory. The rpath now lists
both.

Two smaller things the same run surfaced:

- makepkg ran its tidying steps on a tree that was already built and
  verified - removing libtool and static library files, purging, compressing
  man pages. For a -bin package that is a difference between what was tested
  and what gets installed. All of them are now disabled.
- /opt/jasp-desktop/bin/JASP was not on PATH; the package now symlinks
  /usr/bin/jasp.

packaging/PKGBUILD.in

@@ -44,10 +44,12 @@ depends=(
   'fontconfig' 'freetype2' 'libxkbcommon' 'hicolor-icon-theme'
 )
 
-# The tarball is a complete /opt + /usr install tree. Stripping would be slow and
-# is a good way to break a bundled R plus several hundred compiled R modules;
-# the rpath set at build time must also survive untouched.
-options=('!strip' '!debug')
+# The tarball is a complete, already-verified /opt + /usr install tree, so every
+# one of makepkg's tidying steps is unwanted here: they would modify content
+# that was tested in exactly this form. Stripping in particular would be slow
+# and is a good way to break a bundled R plus several hundred compiled R
+# modules, and the rpath set at build time must survive untouched.
+options=('!strip' '!debug' '!libtool' '!staticlibs' '!zipman' '!purge' '!emptydirs')
 
 source=("jasp-desktop-${pkgver}-${pkgrel}-x86_64.tar.zst::@DOWNLOAD_URL@")
 sha256sums=('@SHA256@')
@@ -55,4 +57,8 @@ sha256sums=('@SHA256@')
 package() {
   cp -a "${srcdir}/opt" "${pkgdir}/opt"
   cp -a "${srcdir}/usr" "${pkgdir}/usr"
+
+  # The application lives under /opt; give it a name on PATH.
+  install -d "${pkgdir}/usr/bin"
+  ln -s /opt/jasp-desktop/bin/JASP "${pkgdir}/usr/bin/jasp"
 }