Fix a syntax error in build.sh

[dgbeliveau]

The correct syntax here is ${VARIABLE:-REPLACEMENT}. The dash is part of the operator.

Since the replacement also needs to start with a dash, two dashes are required.

For instance:

CMAKE_OPTS="${CMAKE_OPTS:-DBUILD_SHARED_LIBS=OFF}"
echo $CMAKE_OPTS

Will output

DBUILD_SHARED_LIBS=OFF

And

CMAKE_OPTS="${CMAKE_OPTS:--DBUILD_SHARED_LIBS=OFF}"
echo $CMAKE_OPTS

Will output

-DBUILD_SHARED_LIBS=OFF

This issue was causing the -DBUILD_SHARED_LIBS=OFF default to be ignored if a user did not set CMAKE_OPTS:

2023-09-06T22:39:53.3228622Z cmake -DMAC_ARCH=x86_64 -DCMAKE_BUILD_TYPE=Debug -DCMAKE_PACKAGE_TYPE=deb -DCMAKE_CXX_FLAGS="-DHAVE_MAT_EVT_TRACEID=1" DBUILD_SHARED_LIBS=OFF ..

CMake Warning:
  Ignoring extra path from command line:

   "/mnt/s/out/DBUILD_SHARED_LIBS=OFF"

[lalitb]

LGTM. Thanks for the fix.

[ThomsonTan]

Thanks for the fix.