Fix SLEEF_BUILD_SCALAR_LIB lost function

[xuhancn]

Fix "SLEEF_BUILD_SCALAR_LIB" lost function to control build sleefscalar lib.

Status	Control Build	Control Install
Current Code	No	Yes
This PR	Yes	Yes

Original code: SLEEF_BUILD_SCALAR_LIB only control whether install scalar_lib, it would always build scalar_lib.
My PR: SLEEF_BUILD_SCALAR_LIB control both whether build and install scalar_lib.

[blapie]

Hi! Could you please give a bit of context?

What do you mean by lost function? Do you mean that library is build but not installed?

I can see a benefit in choosing to build scalar libs or not, especially if they are not installed after all.

Just a quick reminder. In the original design, scalar routines are not meant to be used but rather here as a reference for vector implementations. So it is recommended not to use them when performance matters.

[xuhancn]

Hi! Could you please give a bit of context?

What do you mean by lost function? Do you mean that library is build but not installed?

I can see a benefit in choosing to build scalar libs or not, especially if they are not installed after all.

Just a quick reminder. In the original design, scalar routines are not meant to be used but rather here as a reference for vector implementations. So it is recommended not to use them when performance matters.

Q: What do you mean by lost function? Do you mean that library is build but not installed?
A: I think SLEEF_BUILD_SCALAR_LIB should like other switch, both control build and install its library. lost function means lost control to build.

Original code: SLEEF_BUILD_SCALAR_LIB only control whether install scalar_lib, it would always build scalar_lib.
My PR: SLEEF_BUILD_SCALAR_LIB control both whether build and install scalar_lib.

update to description also.