Fix foss toolchains syntax in spack_setup

closes #106

toolchains/foss2022a-cuda-mpi/spack.yaml

 spack:
   definitions:
   - compilers:
-    - ##TOOLCHAIN_COMPILER##
+    - "##TOOLCHAIN_COMPILER##"
   - mpis:
     - openmpi@4.1.4+cuda cuda_arch=70 fabrics=ucx schedulers=slurm ^slurm@20-11-4-1+pmix^ucx@1.13.1+cma+cuda+dc+dm+gdrcopy+ib_hw_tm+knem+mlx5_dv+rc+rdmacm+thread_multiple+ud+verbs+vfs~xpmem
       ^cuda@11.4+allow-unsupported-compilers

toolchains/foss2022a-mpi/spack.yaml

 spack:
   definitions:
   - compilers:
-    - ##TOOLCHAIN_COMPILER##
+    - "##TOOLCHAIN_COMPILER##"
   - mpis:
     - openmpi@4.1.4~cuda fabrics=ucx schedulers=slurm ^slurm@20-11-4-1+pmix^ucx@1.13.1+cma~cuda+dc+dm~gdrcopy+ib_hw_tm+knem+mlx5_dv+rc+rdmacm+thread_multiple+ud+verbs+vfs~xpmem
   - packages:

toolchains/foss2022a-serial/spack.yaml

 spack:
   definitions:
   - compilers:
-    - ##TOOLCHAIN_COMPILER##
+    - "##TOOLCHAIN_COMPILER##"
   - packages:
     - binutils@2.38+headers+ld
     - fftw@3.3.10+openmp~~mpi

toolchains/foss2022b-mpi/compiler_vars.sh

-TOOLCHAIN_COMPILER="gcc@12.2.0"
+toolchain_compiler_package="gcc@12.2.0"
+export TOOLCHAIN_COMPILER=$toolchain_compiler_package

toolchains/foss2022b-mpi/spack.yaml

 spack:
   definitions:
   - compilers:
-    - ##TOOLCHAIN_COMPILER##
+    - "##TOOLCHAIN_COMPILER##"
   - mpis:
     - openmpi@4.1.4~cuda fabrics=ucx schedulers=slurm ^slurm@20-11-4-1+pmix^ucx@1.13.1+cma~cuda+dc+dm~gdrcopy+ib_hw_tm+knem+mlx5_dv+rc+rdmacm+thread_multiple+ud+verbs+vfs~xpmem
   - packages:

toolchains/foss2022b-serial/spack.yaml

 spack:
   definitions:
   - compilers:
-    - ##TOOLCHAIN_COMPILER##
+    - "##TOOLCHAIN_COMPILER##"
   - packages:
     - binutils@2.39+headers+ld
     - fftw@3.3.10+openmp~mpi~pfft_patches

toolchains/foss2023a-mpi/spack.yaml

 spack:
   definitions:
   - compilers:
-    - ##TOOLCHAIN_COMPILER##
+    - "##TOOLCHAIN_COMPILER##"
   - mpis:
     - openmpi@4.1.5~cuda fabrics=ucx schedulers=slurm ^slurm@20-11-4-1+pmix^ucx@1.13.1+cma~cuda+dc+dm~gdrcopy+ib_hw_tm+knem+mlx5_dv+rc+rdmacm+thread_multiple+ud+verbs+vfs~xpmem
   - packages:

toolchains/foss2023a-serial/spack.yaml

 spack:
   definitions:
   - compilers:
-    - ##TOOLCHAIN_COMPILER##
+    - "##TOOLCHAIN_COMPILER##"
   - packages:
     - binutils@2.40+headers+ld
     - fftw@3.3.10+openmp~mpi~pfft_patches

toolchains/foss2023b-mpi/compiler_vars.sh

-TOOLCHAIN_COMPILER="gcc@13.2.0"
+toolchain_compiler_package="gcc@13.2.0"
+export TOOLCHAIN_COMPILER=$toolchain_compiler_package

toolchains/foss2023b-mpi/spack.yaml

 spack:
   definitions:
   - compilers:
-    - ##TOOLCHAIN_COMPILER##
+    - "##TOOLCHAIN_COMPILER##"
   - mpis:
     - openmpi@4.1.6~cuda fabrics=ucx schedulers=slurm ^slurm@20-11-4-1+pmix^ucx@1.14.1+cma~cuda+dc+dm~gdrcopy+ib_hw_tm+knem+mlx5_dv+rc+rdmacm+thread_multiple+ud+verbs+vfs~xpmem
   - packages:

toolchains/foss2023b-serial/spack.yaml

 spack:
   definitions:
   - compilers:
-    - ##TOOLCHAIN_COMPILER##
+    - "##TOOLCHAIN_COMPILER##"
   - packages:
     - binutils@2.40+headers+ld
     - fftw@3.3.10+openmp~mpi+pfft_patches