Static build fails when using tarballs instead of submodules due to missing lcms

[olepbr]

Describe the bug

Trying to build jpegli with -DJPEGXL_STATIC=ON only succeeds if third party dependencies have been fetched using git submodule update --init. When building from a tarball, which causes deps.sh to fetch tarballs for the dependencies, the build fails because it cannot locate lcms:

-- Could NOT find LCMS2 (missing: LCMS2_LIBRARY LCMS2_INCLUDE_DIR) (Required is at least version "2.12")
CMake Error at third_party/CMakeLists.txt:62 (message):
  Please install lcms2 or run git submodule update --init

A workaround for this bug is to build using skcms instead, by passing -DJPEGXL_ENABLE_SKCMS=ON.

To Reproduce

1. Download a tarball of this repo at a specific commit, e.g. wget https://github.com/google/jpegli/archive/9e21f7e38283fe0837be763e02d97b7f4988831f.tar.gz
2. Extract it: tar -xaf 9e21f7e38283fe0837be763e02d97b7f4988831f.tar.gz
3. Enter the directory cd jpegli-9e21f7e38283fe0837be763e02d97b7f4988831f
4. Fetch third party dependencies: ./deps.sh
5. Attempt to build: SKIP_TEST=1 ./ci.sh release -DJPEGXL_STATIC=ON

Dockerfile doing the above:

FROM debian:bookworm
ARG DEBIAN_FRONTEND=noninteractive
RUN apt-get update && apt-get -y full-upgrade && \
    apt-get install -y \
    ca-certificates \
    clang \
    cmake \
    curl \
    doxygen \
    extra-cmake-modules \
    g++ \
    git \
    graphviz \
    libgif-dev \
    libgoogle-perftools-dev \
    libjpeg-dev \
    ninja-build

WORKDIR /root

ARG JPEGLI_SHA=9e21f7e38283fe0837be763e02d97b7f4988831f
ARG JPEGLI_VERSION=jpegli-${JPEGLI_SHA}
ENV SKIP_TEST=1
ADD https://github.com/google/jpegli/archive/${JPEGLI_SHA}.tar.gz .
RUN tar -xaf ./${JPEGLI_SHA}.tar.gz && \
    cd ./${JPEGLI_VERSION} && \
    ./deps.sh && \
    ./ci.sh release -DJPEGXL_STATIC=ON

Expected behavior

A successful jpegli build, with statically linked binaries in build/tools.

Environment

• OS: Debian 12 "bookworm"
• Compiler version: clang 14.0.6
• CPU type: aarch64
• cjxl/djxl version string: not applicable, i think

Additional context

One problem is that deps.sh does not download a lcms tarball (there's no THIRD_PARTY_LCMS variable specifying the revision to use, nor an appropriate download_github invocation). Secondly, there are some problems in third_party/CMakeLists.txt:

1. To determine if lcms in the repo, the code checks whether "${CMAKE_CURRENT_SOURCE_DIR}/lcms/.git"exists; .git is not included in GitHub's tarballs, hence this consistently fails unless lcms is fetched as a submodule. Fix: check for a file that actually is included, like .gitignore.
2. The code attempts to call configure_file() on third_party/lcms/COPYING, a file which does not exist (it's somehow created when using submodules, but I don't understand how).

In summary, this is the changes needed in order to make the build succeed (just commenting out configure_file() is not really an acceptable solution, but I'm not sure what the correct way to fix this is).

diff --git a/deps.sh b/deps.sh
index 00395390..1b638081 100755
--- a/deps.sh
+++ b/deps.sh
@@ -23,6 +23,7 @@ THIRD_PARTY_SJPEG="e5ab13008bb214deb66d5f3e17ca2f8dbff150bf"
 THIRD_PARTY_ZLIB="51b7f2abdade71cd9bb0e7a373ef2610ec6f9daf" # v1.3.1
 THIRD_PARTY_LIBPNG="f135775ad4e5d4408d2e12ffcc71bb36e6b48551" # v1.6.40
 THIRD_PARTY_LIBJPEG_TURBO="8ecba3647edb6dd940463fedf38ca33a8e2a73d1" # 2.1.5.1
+THIRD_PARTY_LCMS="5176347635785e53ee5cee92328f76fda766ecc6"
 
 # Download the target revision from GitHub.
 download_github() {
@@ -91,6 +92,7 @@ EOF
   download_github third_party/zlib madler/zlib
   download_github third_party/libpng glennrp/libpng
   download_github third_party/libjpeg-turbo libjpeg-turbo/libjpeg-turbo
+  download_github third_party/lcms mm2/Little-CMS
   echo "Done."
 }
 
diff --git a/third_party/CMakeLists.txt b/third_party/CMakeLists.txt
index 9bd1b8c9..be75981f 100644
--- a/third_party/CMakeLists.txt
+++ b/third_party/CMakeLists.txt
@@ -56,15 +56,15 @@ if (JPEGXL_ENABLE_SKCMS)
                  ${PROJECT_BINARY_DIR}/LICENSE.skcms COPYONLY)
 endif ()
 if (NOT JPEGXL_ENABLE_SKCMS)
-  if( NOT EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/lcms/.git" OR JPEGXL_FORCE_SYSTEM_LCMS2 )
+  if( NOT EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/lcms/.gitignore" OR JPEGXL_FORCE_SYSTEM_LCMS2 )
     find_package(LCMS2 2.12)
     if ( NOT LCMS2_FOUND )
       message(FATAL_ERROR "Please install lcms2 or run git submodule update --init")
     endif ()
   else()
     include(lcms2.cmake)
-    configure_file("${CMAKE_CURRENT_SOURCE_DIR}/lcms/COPYING"
-                   ${PROJECT_BINARY_DIR}/LICENSE.lcms COPYONLY)
+    #configure_file("${CMAKE_CURRENT_SOURCE_DIR}/lcms/COPYING"
+    #               ${PROJECT_BINARY_DIR}/LICENSE.lcms COPYONLY)
   endif()
 endif()