Stage the OpenBLAS install in the builder and just COPY the files

[coderabbitai]

Problem Description

During ppc64le builds of the jupyter-datascience image, OpenBLAS installation fails with permission errors when attempting to install directly into /usr/local during the final stage. Build logs from PR #2460 show:

• cc1: fatal error: can't open 'ctest1.s' for writing: Permission denied
• /usr/bin/ld: cannot open output file getarch: Permission denied
• mkdir: cannot create directory '/usr/local/lib/cmake': Permission denied
• Writing /usr/local/include/openblas_config.h failed

The current implementation in jupyter/datascience/ubi9-python-3.12/Dockerfile.cpu (lines 206-221) builds OpenBLAS in the openblas-builder stage but attempts installation in the final jupyter-datascience stage, causing permission conflicts.

Root Cause Analysis

1. Multi-stage permission mismatch: OpenBLAS build artifacts are copied as source code, then make install runs in final stage
2. Runtime permission conflicts: Final stage USER 1001 cannot write to /usr/local system paths
3. Architecture-specific complexity: Issue only affects ppc64le where OpenBLAS compilation is required

Proposed Solution

Recommended Approach: Stage the complete installation within the builder stage using DESTDIR pattern:

# In openblas-builder stage
source /opt/rh/gcc-toolset-13/enable
make -j$(nproc) TARGET=POWER9 BINARY=64 USE_OPENMP=1 USE_THREAD=1 NUM_THREADS=120 DYNAMIC_ARCH=1 INTERFACE64=0
make -j$(nproc) PREFIX=/usr/local DESTDIR=/openblas-root install

# In final stage  
COPY --from=openblas-builder /openblas-root/usr/local /usr/local

Alternative Approaches

1. Custom prefix approach: Install to builder-specific path and copy selectively
2. Archive approach: Create tar archive in builder, extract in final stage

Acceptance Criteria

• OpenBLAS builds successfully in openblas-builder stage with DESTDIR staging
• Installation artifacts are copied cleanly to final stage without permission errors
• ppc64le builds complete successfully without OpenBLAS-related failures
• Non-ppc64le architectures continue to work with placeholder/skip logic
• Build time remains reasonable (no significant performance regression)
• Runtime functionality verified - OpenBLAS libraries accessible to Python packages
• Multi-architecture CI builds pass consistently

Implementation Guidance

1. Modify openblas-builder stage to use DESTDIR pattern for installation staging
2. Update final stage COPY commands to transfer staged artifacts from builder
3. Ensure proper file ownership/permissions during COPY operation
4. Verify PKG_CONFIG_PATH environment variable remains functional
5. Test integration with NumPy, SciPy and other OpenBLAS-dependent packages

Context

• PR: ppc64le: implement datascience jupyter image build on ppc64le (#2406) #2460 (ppc64le datascience jupyter image implementation)
• Comment: ppc64le: implement datascience jupyter image build on ppc64le (#2406) #2460 (comment)
• Architecture: ppc64le multi-architecture support
• Component: jupyter/datascience/ubi9-python-3.12/Dockerfile.cpu

This issue addresses systematic infrastructure reliability improvements for Power architecture support in ODH notebook images.