libclc: fix install path nesting + relocate libclc.pc to lib/pkgconfig

Install used an ABSOLUTE CMAKE_INSTALL_PREFIX (${COOKBOOK_STAGE}/usr) together
with DESTDIR=${COOKBOOK_STAGE}/stage, so everything double-nested under
stage.tmp/<abs>/stage.tmp/usr/... and libclc.pc/.bc never reached the expected
paths. Use the standard pattern: relative prefix /usr + DESTDIR=${COOKBOOK_STAGE}
(libclc.pc gets prefix=/usr, resolved downstream via PKG_CONFIG_SYSROOT_DIR);
drop the stage-flatten hack. Also relocate libclc.pc from share/pkgconfig
(upstream's DATADIR) to lib/pkgconfig (cookbook convention mesa looks up).
All 2610 GPU bitcode files already generate + install correctly.

local/recipes/dev/libclc/recipe.toml

@@ -157,7 +157,7 @@ COOKBOOK_CMAKE_FLAGS+=(
     -DLIBCLC_STANDALONE_BUILD=TRUE
     -DLIBCLC_TARGETS_TO_BUILD="r600--;amdgcn--;amdgcn--amdhsa;amdgcn-mesa-mesa3d"
     -DENABLE_RUNTIME_SUBNORMAL=OFF
-    -DCMAKE_INSTALL_PREFIX="${COOKBOOK_STAGE}/usr"
+    -DCMAKE_INSTALL_PREFIX=/usr
     -DCMAKE_INSTALL_LIBDIR=lib
     -DCMAKE_INSTALL_INCLUDEDIR=include
     -DCMAKE_INSTALL_DATADIR=share
@@ -185,15 +185,14 @@ fi
 # on PATH for the ninja run.
 export PATH="$(pwd):${PATH}"
 "${COOKBOOK_NINJA}" -j"${COOKBOOK_MAKE_JOBS}"
-DESTDIR="${COOKBOOK_STAGE}/stage" "${COOKBOOK_NINJA}" install
-
-# Move installed files from $COOKBOOK_STAGE/stage to $COOKBOOK_STAGE.
-# The DESTDIR install above places everything under
-# $COOKBOOK_STAGE/stage; flatten the extra stage dir.
-if [ -d "${COOKBOOK_STAGE}/stage" ]; then
-    cp -a "${COOKBOOK_STAGE}/stage/." "${COOKBOOK_STAGE}/"
-    rm -rf "${COOKBOOK_STAGE}/stage"
-fi
+# Standard install: RELATIVE prefix (/usr, set in COOKBOOK_CMAKE_FLAGS) +
+# DESTDIR=${COOKBOOK_STAGE} -> files land at ${COOKBOOK_STAGE}/usr/... and the
+# generated libclc.pc carries prefix=/usr, which the downstream mesa build
+# resolves via PKG_CONFIG_SYSROOT_DIR. (The previous absolute prefix +
+# DESTDIR/stage double-nested everything under
+# stage.tmp/<abs>/stage.tmp/usr/... so libclc.pc was never at the expected
+# path.)
+DESTDIR="${COOKBOOK_STAGE}" "${COOKBOOK_NINJA}" install
 
 # Restore the cross-compile env for any subsequent (cross) steps. The native
 # cmake/ninja above MUST run with the clean (unset) env, so this restore is
@@ -208,6 +207,16 @@ export CPPFLAGS="$_SAVED_CPPFLAGS"
 # The cmake install above places them at $COOKBOOK_STAGE/usr/share/clc
 # which is the right path; no further action needed.
 
+# Upstream libclc installs libclc.pc under share/pkgconfig (its DATADIR);
+# relocate it to lib/pkgconfig, the cookbook convention that mesa's
+# dependency('libclc') pkg-config lookup uses.
+if [ -f "${COOKBOOK_STAGE}/usr/share/pkgconfig/libclc.pc" ] \
+   && [ ! -f "${COOKBOOK_STAGE}/usr/lib/pkgconfig/libclc.pc" ]; then
+    mkdir -p "${COOKBOOK_STAGE}/usr/lib/pkgconfig"
+    mv "${COOKBOOK_STAGE}/usr/share/pkgconfig/libclc.pc" \
+       "${COOKBOOK_STAGE}/usr/lib/pkgconfig/libclc.pc"
+fi
+
 if [ ! -f "${COOKBOOK_STAGE}/usr/lib/pkgconfig/libclc.pc" ]; then
     echo "libclc: ERROR — install did not produce libclc.pc" >&2
     echo "libclc: expected at ${COOKBOOK_STAGE}/usr/lib/pkgconfig/libclc.pc" >&2