diff --git a/.github/workflows/spack_docker_images.yml b/.github/workflows/spack_docker_images.yml
index a5683ce..83a52e0 100644
--- a/.github/workflows/spack_docker_images.yml
+++ b/.github/workflows/spack_docker_images.yml
@@ -141,3 +141,4 @@ jobs:
           LIBS=${{ matrix.level }}
         tags: |
           ${{ steps.info.outputs.fullspack }}
+          
\ No newline at end of file
diff --git a/spack/3-baselibs/Dockerfile b/spack/3-baselibs/Dockerfile
index 11af49c..4085f9a 100644
--- a/spack/3-baselibs/Dockerfile
+++ b/spack/3-baselibs/Dockerfile
@@ -36,22 +36,37 @@ ARG COMPILER
 ARG SPACK_INSTALL_ARGS="--show-log-on-error --fail-fast"
 
 # Install the spack compiler with our latest system compiler
-COPY ${COMPILER}.lst compilerpkg.lst
-RUN spack solve -I -U \
-          "$(cat compilerpkg.lst)%$(spack compilers | tr ' ' '\n' | grep @)" \
- && spack install ${SPACK_INSTALL_ARGS} -U \
-          "$(cat compilerpkg.lst)%$(spack compilers | tr ' ' '\n' | grep @)"
-
-
-# Prevent building any new compiler
-RUN spack config --scope site add 'packages:llvm:buildable: false'
-RUN spack config --scope site add 'packages:gcc:buildable: false'
+COPY ${COMPILER}.lst compilerpkg.lst 
+RUN <<'EORUN'
+set -e
+COMPILER_PKG="$(cat compilerpkg.lst)"
+SPACK_VERSION="$(spack compilers | tr ' ' '\n' | grep @)"
+# Select the ~bootstrap gcc variant as the 3-stage bootstrap fails on latest spack
+if [[ "$COMPILER_PKG" == gcc* ]]
+then
+  COMPILER_SPECIFIC_VARIANTS="~bootstrap"
+else
+  COMPILER_SPECIFIC_VARIANTS=""
+fi
+spack solve -I -U ${COMPILER_PKG}${COMPILER_SPECIFIC_VARIANTS}%${SPACK_VERSION} \
+  && spack install ${SPACK_INSTALL_ARGS} -U "${COMPILER_PKG}${COMPILER_SPECIFIC_VARIANTS}%${SPACK_VERSION}"
+EORUN
 
+# Prevent building any new compiler and set compiler flags for doxygen to support LTO 
+RUN <<'EORUN'
+set -e
+spack config --scope site add "packages:llvm:buildable:false"
+spack config --scope site add "packages:gcc:buildable:false"
+if spack --version | grep -qs '^1\.' && spack find llvm &>/dev/null
+then
+  spack config --scope site add "packages:doxygen:require:ldflags=-fuse-ld=lld"
+fi
+EORUN
 
 # Generate a compiler ref
 # * before 1.0, rely on the compilers section and generate a mixed compiler for llvm
 # * from spack 1.0 on, define a toolchain
-RUN <<EORUN
+RUN <<'EORUN'
 set -e
 if ( spack --version | grep -qs '^1\.' )
 then
@@ -86,39 +101,42 @@ else
 fi
 EORUN
 
-
-# Install an environment with our base libraries using the compiler ref we just generated
+# Create an environment with our base libraries using the compiler ref we just generated
 COPY <<'EOCOPY' spack.yaml
 spack:
   view: false
   definitions:
   - buildeps: []
-  - compiler: []
   - libs: []
   - mpi: []
   - mpilibs: []
   specs:
-  - '$buildeps'
-  - matrix:
-    - ['$%compiler']
-    - - '$libs'
-      - '$mpi'
-  - matrix:
-    - ['$%compiler']
-    - ['$^mpi']
-    - ['$mpilibs']
+  - $buildeps
+  - $libs
+  - $mpi
+  - $mpilibs
 EOCOPY
 RUN spack env create pdienv spack.yaml
 COPY deps.sh deps.sh
-RUN . deps.sh && spack -e pdienv add -l buildeps ${BASE_BUILDDEPS}
-RUN . deps.sh && spack -e pdienv add -l libs     ${BASE_LIBS}
-RUN <<EORUN
+
+# The toolchain is attached directly to each lib spec (string-parsed), which
+# avoids the matrix that crashes in expand_toolchains on latest spack
+RUN <<'EORUN'
 set -e
-if ( spack --version | grep -qs '^1\.' )
-then spack -e pdienv add -l compiler pditoolchain
-else spack -e pdienv add -l compiler "$(spack compilers | tr ' ' '\n' | grep @)"
+. deps.sh
+if spack --version | grep -qs '^1\.'
+then COMPILER_REF="%pditoolchain"
+else COMPILER_REF="%$(spack compilers | tr ' ' '\n' | grep @)"
 fi
+for p in ${BASE_BUILDDEPS}; do
+  spack -e pdienv add -l buildeps "$p"
+done
+for p in ${BASE_LIBS}; do
+  spack -e pdienv add -l libs "$p ${COMPILER_REF}"
+done
 EORUN
+
+# Concretize, fetch, install 
 RUN spack -e pdienv concretize --reuse
 RUN spack -e pdienv fetch \
  || spack -e pdienv fetch \
diff --git a/spack/3-baselibs/clang.lst b/spack/3-baselibs/clang.lst
index 39f235a..bb03dfc 100644
--- a/spack/3-baselibs/clang.lst
+++ b/spack/3-baselibs/clang.lst
@@ -1 +1 @@
-llvm+llvm_dylib+link_llvm_dylib~lldb
+llvm+llvm_dylib+link_llvm_dylib+lld~lldb
diff --git a/spack/4-mini/Dockerfile b/spack/4-mini/Dockerfile
index 911dcbf..5f91f20 100644
--- a/spack/4-mini/Dockerfile
+++ b/spack/4-mini/Dockerfile
@@ -15,4 +15,4 @@ ARG SPACK_INSTALL_ARGS="--show-log-on-error --fail-fast"
 RUN              spack -e pdienv add -l mpi    "${MPI}"
 RUN . deps.sh && spack -e pdienv add -l mpilibs ${BASE_MPILIBS}
 RUN spack -e pdienv concretize -f --reuse
-RUN spack -e pdienv install ${SPACK_INSTALL_ARGS}
+RUN spack -e pdienv install ${SPACK_INSTALL_ARGS}
\ No newline at end of file
diff --git a/spack/5-all/Dockerfile b/spack/5-all/Dockerfile
index 345ebf3..04624d0 100644
--- a/spack/5-all/Dockerfile
+++ b/spack/5-all/Dockerfile
@@ -26,4 +26,4 @@ ARG SPACK_INSTALL_ARGS="--show-log-on-error --fail-fast"
 RUN . deps.sh && spack -e pdienv add -l libs    ${OPT_LIBS}
 RUN . deps.sh && spack -e pdienv add -l mpilibs ${OPT_MPILIBS}
 RUN spack -e pdienv concretize -f  --reuse
-RUN spack -e pdienv install ${SPACK_INSTALL_ARGS}
+RUN spack -e pdienv install ${SPACK_INSTALL_ARGS}
\ No newline at end of file
diff --git a/spack/6-finalize/Dockerfile b/spack/6-finalize/Dockerfile
index b1d9585..957a066 100644
--- a/spack/6-finalize/Dockerfile
+++ b/spack/6-finalize/Dockerfile
@@ -173,4 +173,4 @@ RUN export VERBOSE=1 \
 
 
 
-FROM main
+FROM main
\ No newline at end of file